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LAST GAS QUIZ: Ideal, Avogadro's, Dalton's and Graham's Law
QuizĀ by Jeoffrey Sanga Delos Reyes
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āThe variables temperature and pressure are held constant in Avogadroās law for gases.
āAvogadroās law states that a gas that increases in moles compresses in direct proportion.
The variables temperature and pressure are held constant in Avogadroās law for gases.
Avogadroās law states that a gas that increases in moles compresses in direct proportion.
Effusion is the escape of molecules in space through another substance by collision
Diffusion is the escape of gas molecules through a tiny hole into space
The standard pressure for which R is based upon is 1 pascal.
The greater the molar mass of a gas, the faster it will effuse
The condition for an ideal gas is set at absolute temperature.
Consider a sample of gas with the following logged data entries:
Determine the moles of gas when it occupies at 15L.
Consider a sample of gas with the following logged data entries:
Which must be true about the gas sample from V1 = 15L to V2 = 25L? (2pts)
Consider a sample of gas with the following logged data entries:
Which law describes the gas sample described in the graph above?
The Ideal gas law is derived from the following relationships of variable except:
Which of the following reasons explains the deviation of a real gas from ideal behavior?
An amount of 76.8 g of oxygen gas is held at a temperature of 97 Ā°C and in a container with a volume of 5500 mL.
How many moles of oxygen gas in the container? (2pts)
An amount of 76.8 g of oxygen gas is held at a temperature of 97 Ā°C and in a container with a volume of 5500 mL.
At what temperature does the oxygen gas held at? (2pts)
An amount of 76.8 g of oxygen gas is held at a temperature of 97 Ā°C and in a container with a volume of 5500 mL.
What is the pressure of the gas in the container? (2pts)
Consider the gas samples in these connected valves:
Which of the gas samples has greater partial pressure when the valves are opened and allowed to mix?
Consider the gas samples in these connected valves:
Which of the gas samples has greater partial pressure when the valves are opened and allowed to mix?
Consider the gas samples in these connected valves:
Considering the pressure at the third valve is 1atm, what is the partial pressure of gas X? (Note: 1 particle = 1 mole) (2pts)
Consider the graph of two gases A and B at the same temperature,
Which of the gases efuses faster?
Consider the graph of two gases A and B at the same temperature, AND suppose these gases are nitrogen and neon,
Which must be gas A?
Consider the graph of two gases A and B at the same temperature, AND suppose these gases are nitrogen and neon,
Which must be gas B?
Consider the graph of two gases A and B at the same temperature, AND suppose these gases are nitrogen and neon,
Considering both gases contained in 100 mL cylinder held at constant pressure and temperature, which of these gases will have greater volume when their initial samples of 100 g each were halved? (2pts)Two balloons were inflated of the same volume of gas, one with hydrogen and one with oxygen. Which of the two balloons will effuse faster?
Which of the following is true of these two gases contained in a rubber balloon? (2pts)
Make a multiple choice quiz for my year 8 science students based on the science in this transcript from a video: 3Ā°C 0:04 It can be the difference between snow and sleet 0:08 Wearing a jacket or not 0:11 In your day-to-day life, it may not seem significant 0:15 But 3Ā°C of global warming would be catastrophic 0:20 Heatwaves, droughts, extreme precipitation, even fire 0:25 3Ā°C of warming is really disastrous 0:28 The scary thing is, the world is well on its way there 0:32 Since the industrial revolution, the Earth has warmed between 1.1Ā°C and 1.3Ā°C 0:40 This is a problem that babies you pass in the street will have to live with 0:46 Children born today... 0:47 ...are up to seven times more likely to face extreme weather than their grandparents 0:52 If global temperatures do rise by 3Ā°C... 0:55 ...what would their world look like? Climate change is already having devastating effects 1:03 Rising sea levels 1:05 Desertification 1:07 Hollywood has always enjoyed imagining the end of the world 1:11 While blockbusters like this are clearly fiction... 1:14 ...this film will show the scenario we all face... 1:17 ...unless more drastic measures are taken to stop burning fossil fuels 1:30 In some parts of the world the effects of inaction are already clear 1:35 The slums of Bangladeshās capital are filling up with climate migrants 1:41 Minara comes from Bhola District, an area in southern Bangladesh 1:46 There, like many other parts of the country... 1:49 ...rivers swollen by heavier rain and melting Himalayan glaciers... 1:53 ...are washing away peopleās homes 1:56 Many, like her, have lost everything 2:00 Our home in Bhola had endless amounts of land 2:03 There was lots of space for farming, we had a spacious house 2:08 There were different types of fruits, vegetation and trees growing at home 2:12 We used to eat the fruit from our own trees 2:18 I canāt eat them now because they don't exist anymore 2:21 Since the river flooded for the third time, I had to flee to Dhaka 2:26 Life was much better back home 2:29 It was unbearable to live through, truly intolerable 2:33 We didnāt have the time to save anything at all 2:38 1.1Ā°C to 1.3Ā°C of global warming has already transformed Minaraās life 2:45 Itās one of the reasons why so many migrants like her... 2:47 ...are moving to the city each year... 2:50 ...nearly 400,000 according to the last estimate 2:53 And climate models show there could be much worse to come How climate modelling works 3:02 Climate scientist Joeri Rogelj... 3:04 ...has spent the last ten years modelling future climate scenarios... 3:08 ...for the United Nations 3:10 The models we use to carry out this exercise... 3:13 ...really represent the state of the art... 3:15 ...of our current knowledge of climate change and where we are heading 3:19 Joeriās projections use data collected by hundreds of scientists around the world 3:26 Here this is the 3Ā°C level... 3:28 ...and so there is at least a one-in-four chance that under current policies... 3:32 ...we would hit 3Ā°C by the end of the century 3:36 This is just one of the scenarios Joeri looks at 3:40 Another one imagines that all policy promises are kept 3:44 The most optimistic assumes that all promises have been kept... 3:47 ...and net-zero targets are met 3:50 Where our best estimate ends up around 2Ā°C at the end of the century... 3:54 ...there is still a one-in-20 chance that we end up with 3Ā°C instead 3:59 One would not be entering a plane if there is a one-in-20 chance... 4:03 ...that the plane will crash Nowhere is safe from global warming 4:07 A rise of 3Ā°C would affect everyone 4:10 Even wealthy cities in rich countries wouldnāt be immune to the consequences 4:15 European capitals like Paris and Berlin... 4:18 ...would bake under more extreme heatwaves 4:22 Frequent storm-surges in New York could turn parts of the city desolate 4:27 In many ways, cities magnify, intensify climate events 4:33 Cities are hotter than the places around them... 4:36 ...they tend to be more vulnerable to flooding 4:39 And you can get a really bad event in a city in a way that you canāt in the countryside 4:46 And because of their denser populations... 4:49 ...disasters in a city affect far more people 4:52 Some cities might be badly prepared for the changes coming 4:56 But they have the means to adapt 4:59 Cities tend to be wealthier than surrounding places 5:03 They have a lot of amenities 5:05 A city that has taken seriously the risks of a 3Ā°C world... 5:08 ā¦wouldnāt necessarily be a worse place to be in a 3Ā°C world 5:12 But a city that hasnāt prepared for these sort of eventualities... 5:16 ...that might be a really nasty place The impact of prolonged droughts 5:20 So far, many developed cities have got off lightly... 5:24 ...but some rural parts of the world are suffering disproportionately 5:29 Smallholdersāsmall-scale farmersāare particularly vulnerable to climate change 5:35 And there are over 600 million around the world 5:38 Smallholders with farms under two hectares... 5:40 ...produce around a third of the global food supply 5:46 Central Americaās āDry Corridorā... 5:48 ...supports a mix of smallholdings and medium-sized farms 5:53 Sandwiched between the Pacific Ocean and the Caribbean Sea... 5:56 ...the area is prone to droughts 6:08 Israel RamĆrez Rivera is a smallholder in Guatemala 6:12 Here, climate change is making the dry seasons longer, and more severe 6:18 This is the biggest ear of maize that this plot could deliver 6:23 He depends on his crops of corn and beans 6:26 But theyāre getting harder to grow 6:30 The surrounding mountains... 6:32 ...used to provide us with native food... 6:38 ...and now that isnāt an option anymore... 6:41 ...due to climate change and its effects 6:46 Nearly two-thirds of the smallholders in the Dry Corridor now live in poverty 6:52 The impact of all of this for us... 6:59 ...malnutrition among children 7:03 Weāve lost a few 7:07 For my crops especially, the midsummer heat is harder than before 7:16 The plant dries up and canāt provide us... 7:19 ...with the necessary food provision 7:24 Severe droughts in Central America... 7:26 ...are now four times more likely than they were last century 7:30 Many families from here have gone to the States 7:37 The economic despair and debts... 7:44 ...have pushed many people from this community to do this journey 7:53 Migration from Guatemala to the United States has quadrupled since 1990 7:59 Not all of this has been due to climate change 8:02 But longer droughts would force even more to move 8:05 In a 3Ā°C world, annual rainfall in this region... 8:09 ...could drop by up to 14% 8:12 At 3Ā°C, over a quarter of the worldās population... 8:16 ...could endure extreme droughts for at least a month of the year 8:19 Northern Africa could see droughts that last for years at a time Rising sea levels, storm surges and flooding 8:24 But for some, too much water will be the problem 8:29 10% of the worldās population lives on a coastline... 8:32 ...thatās less than 10 metres above sea level 8:35 For these coastal inhabitants, a 3Ā°C world would spell disaster 8:40 By 2100, global sea levels could have climbed by half a metre from 2005 levels 8:46 Low-lying cities like Lagos would be especially vulnerable... 8:49 ...with up to up to a third of the population displaced 8:54 And in Fiji, rising waters are already upending lives 9:04 You can see the graveyard there, itās all under water now... 9:08 ...due to this rising sea level and climate change 9:15 The village of Togoru in Fiji is being swallowed by the sea 9:19 Barney Dunn, the village headman, has seen over half the village disappear 9:24 Relativesā houses have been abandoned, and family graves are now under water 9:29 We have been asked by the government to relocate... 9:32 ...but no one wants to relocate... 9:34 ...because we have our great-great-grandparents down there in the sea 9:39 This is the place weāve been brought up in 9:41 ...itās not easy to leave 9:44 Past attempts to build a seawall havenāt worked 9:48 But Barney sees building a new one as the villageās only hope 9:52 If they do that, maybe we can save whatever is left 9:56 But if we donāt have the seawall, then it will be keep eroding and time will come... 10:01 ...maybe in ten,15 years, Togoru will be all eroded 10:05 Rising seas also mean storms cause more floods 10:11 And many more countries could suffer 10:14 The Philippines and Myanmar are just two countries... 10:17 ...that will also see an increase in storm surges in a 3Ā°C world 10:21 To escape, many will moveā¦ 10:24 ā¦often, to urban areas Extreme heat and wet-bulb temperatures 10:27 Half the worldās population already lives in cities... 10:31 ...almost a third in slums 10:36 For them, a 3Ā°C world could be deadly 10:40 Minara has moved to Dhaka to escape the impact of climate change 10:44 But life could get even worse for her 10:47 Iām struggling a lot nowadays 10:49 The heat during the day is unbearable 10:52 Even late at night it doesnāt cool down 10:57 The heat is getting more intense every day 10:59 I mean, itās going to get much worse 11:03 I can barely survive it now, how will I live through it in the future? 11:08 Dhaka is getting hotter 11:11 In the last 20 years the average daytime temperature... 11:13 ...has crept up by nearly half a degree 11:17 Days that approach 40Ā°C are now being reported 11:20 And high so-called wet-bulb temperatures are on the rise 11:26 A wet-bulb temperature is a measure of heat and humidity 11:30 Humans cool themselves by sweatingā¦ 11:32 But in these conditions, when relative humidity is near 100%... 11:36 ...sweat doesnāt evaporate well 11:38 So people canāt cool downā¦ 11:41 ...even if given unlimited shade and water 11:45 At a high wet-bulb temperature, the body canāt lose heat... 11:49 ...and so it gets hotter and hotter... 11:51 ...and the body is designed to work at a given temperature 11:53 And if it gets too hot inside, you will die 11:58 The human limit for wet-bulb temperatures is 35Ā°C... 12:02 ...around skin temperature 12:04 Dhaka will have a much higher chance... 12:05 ...of reaching dangerous wet-bulb temperatures... 12:07 ...if global warming reaches 3Ā°C 12:12 You canāt really adapt to that 12:14 You have to get out. If the temperature is so high that you canāt work... 12:20 ...canāt do hard manual labour outside for significant parts of the year... 12:25 ...then many places will become functionally no longer part of the economy 12:33 Jacobabad in Pakistan, and Ras al Khaimah, in the United Arab Emirates... 12:37 ...have already recorded deadly wet-bulb temperatures 12:40 More of the tropics and the Persian Gulf... 12:43 ...as well as parts of Mexico and the south-eastern United States... 12:47 ...could all get to this threshold by the end of the century 12:50 Climate modelling might show us the weather Increased migration and conflict 12:52 But it doesnāt show us its other effects on society 12:56 Established migration patterns could change 12:59 Climate disasters may exacerbate reasons people cross borders 13:03 Within countries, more people will move to cities 13:07 In a 3Ā°C world, tens of millions of people a year... 13:10 ...could be displaced by disasters made worse by climate change 13:15 When people are displaced by climate... 13:18 ā¦they may well go to cities... 13:19 ...because cities are the places that attract people from the countryside already 13:25 A lot of people who can get to the developed world... 13:28 ...not least because the developed world tends to be less hot, will give that a go 13:35 As migration around the world increases... 13:38 ...there could be more competition for fewer resources 13:42 Waterāalready a highly contested resourceāwill be a focal point 13:47 Turkeyās new Ilisu dam has reduced the flow of water into Iraq 13:53 China lays claim to rivers vital to India and Pakistan 13:57 The prospect of a water-conflict makes people very uneasy 14:03 How national tensions would exacerbate those sorts of reactions... 14:08 ...in a 3Ā°C world... 14:09 ...is the sort of thing that no one should really want to find out 14:14 I think youād have to be incredibly sanguine... 14:16 ...not to think that the sort of climate extremes that we talk about... 14:19 ...in a 3Ā°C world wouldnāt lead some places... 14:22 ...to the brink of societal collapse 14:25 Those lucky enough to escape unrest... Adaptation and mitigation are crucial 14:28 ...would still have to adapt to a radically different world 14:32 People can adapt to climate change in all sorts of ways, one of the most obvious ones... 14:37 ...is air conditioning 14:39 But other ways to adapt at a local or regional level... 14:42 ...I mean, one of the most obvious is diversifying agriculture 14:47 There are physical things you can do, like seawalls 14:52 The fact that people can adapt and that adaptation will reduce suffering... 14:57 ...doesnāt mean that it will eliminate suffering 15:00 Suffering is built into this whole process of heating up the planet 15:06 Adaptation will only get the world so far 15:09 The best way to deal with a 3Ā°C world... 15:12 ...is not to go to a 3Ā°C world 15:14 And thatās why increasing efforts on mitigation are important 15:17 Itās why working towards negative emissions... 15:20 ...that could bring down the temperature after it peaks are important 15:25 Once you get to a 3Ā°C world, you are in real bad global trouble 15:33 The scale of change needed... 15:35 ...and the slow progress of governments so far... 15:38 ...means 3Ā°C of warming is uncomfortably likely unless more is done 15:44 Despite existing pledges, greenhouse-gas emissions... 15:48 ...are still set to rise by 16% from 2010 levels by 2030 15:54 The need to act has never been clearer 15:57 Thereās still time to reduce emissions, so that a 3Ā°C world remains fiction... 16:02 ...rather than becoming factJAKARTA, Indonesia (AP) ā Indonesiaās highest volcano on its most densely populated island released searing gas clouds and rivers of lava Sunday in its latest eruption. Monsoon rains eroded and finally collapsed the lava dome atop 3,676-meter (12,060-foot) Mount Semeru, causing the eruption, according to National Disaster Management Agency spokesperson Abdul Muhari. Several villages were blanketed with falling ash, blocking out the sun, but no casualties have been reported. Several hundred residents, their faces smeared with volcanic dust and rain, fled to temporary shelters or left for other safe areas. Thick columns of ash were blasted more than 1,500 meters (nearly 5,000 feet) into the sky while searing gas and lava flowed down Semeruās slopes toward a nearby river. Increased activities of the volcano on Sunday afternoon prompted authorities to widen the danger zone to 8 kilometers (5 miles) from the crater, said Hendra Gunawan, who heads the Volcanology and Geological Hazard Mitigation Center. He said scientists raised the volcanoās alert level to the highest and people were advised to keep off the southeastern sector along the Besuk Kobokan River, which is in the path of the lava flow. Semeruās last major eruption was in December last year, when it blew up with fury that left 51 people dead in villages that were buried in layers of mud. Several hundred others suffered serious burns and the eruption forced the evacuation of more than 10,000 people. The government moved about 2,970 houses out of the danger zone. Semeru, also known as Mahameru, has erupted numerous times in the past 200 years. Still, as is the case with many of the 129 active volcanoes in Indonesia, tens of thousands of people continue to live on its fertile slopes. Indonesia, an archipelago of more than 270 million people, sits along the Pacific āRing of Fire,ā a horseshoe-shaped series of fault lines, and is prone to earthquakes and volcanic activity.1. Sit down ā Sit on a chair or lower your body. Example: "Please sit down and relax." (Š”ŃŠ“ŃŃŠµ Šø ŃŠ°ŃŃŠ»Š°Š±ŃŃŠµŃŃ.) 2. Lie down ā Recline or rest horizontally. Example: "You should lie down if you're tired." (Š¢ŠµŠ±Šµ ŃŠ»ŠµŠ“ŃŠµŃ ŠæŃŠøŠ»ŠµŃŃ, ŠµŃŠ»Šø ŃŃ ŃŃŃŠ°Š».) 3. Turn down ā Refuse an offer or reduce volume/heat. Example: "She turned down the job offer." (ŠŠ½Š° Š¾ŃŠŗŠ°Š·Š°Š»Š°ŃŃ Š¾Ń ŠæŃŠµŠ“Š»Š¾Š¶ŠµŠ½ŠøŃ Š¾ ŃŠ°Š±Š¾ŃŠµ.) 4. Slow down ā Reduce speed. Example: "Slow down! The road is icy." (Š”Š±Š°Š²Ń ŃŠŗŠ¾ŃŠ¾ŃŃŃ! ŠŠ¾ŃŠ¾Š³Š° ŃŠŗŠ¾Š»ŃŠ·ŠŗŠ°Ń.) 5. Calm down ā Become less angry or anxious. Example: "Calm down and tell me what happened." (Š£ŃŠæŠ¾ŠŗŠ¾Š¹ŃŃ Šø ŃŠ°ŃŃŠŗŠ°Š¶Šø, ŃŃŠ¾ ŃŠ»ŃŃŠøŠ»Š¾ŃŃ.) 6. Break down ā Stop working (machine) or lose control emotionally. Example: "My car broke down yesterday." (ŠŠ¾Ń Š¼Š°ŃŠøŠ½Š° ŃŠ»Š¾Š¼Š°Š»Š°ŃŃ Š²ŃŠµŃŠ°.) 7. Write down ā Record something on paper. Example: "Write down the phone number." (ŠŠ°ŠæŠøŃŠø Š½Š¾Š¼ŠµŃ ŃŠµŠ»ŠµŃŠ¾Š½Š°.) 8. Put down ā Place something on a surface or insult someone. Example: "Put down the book on the table." (ŠŠ¾Š»Š¾Š¶Šø ŠŗŠ½ŠøŠ³Ń Š½Š° ŃŃŠ¾Š».) 9. Bring down ā Reduce (prices, temperature) or make someone sad. Example: "The news brought her down." (ŠŠ¾Š²Š¾ŃŃŃ ŃŠ°ŃŃŃŃŠ¾ŠøŠ»Š° ŠµŠµ.) 10. Cut down ā Reduce consumption (e.g., food, expenses). Example: "I need to cut down on sugar." (ŠŠ½Šµ Š½ŃŠ¶Š½Š¾ ŃŠ¾ŠŗŃŠ°ŃŠøŃŃ ŠæŠ¾ŃŃŠµŠ±Š»ŠµŠ½ŠøŠµ ŃŠ°Ń
Š°ŃŠ°.) 11. Let down ā Disappoint someone. Example: "He let me down by not coming." (ŠŠ½ Š¼ŠµŠ½Ń ŠæŠ¾Š“Š²ŠµŠ», Š½Šµ ŠæŃŠøŠ¹Š“Ń.) 12. Shut down ā Close a business or turn off a machine. Example: "The factory shut down last year." (Š¤Š°Š±ŃŠøŠŗŠ° Š·Š°ŠŗŃŃŠ»Š°ŃŃ Š² ŠæŃŠ¾ŃŠ»Š¾Š¼ Š³Š¾Š“Ń.) 13. Knock down ā Demolish or hit someone to the ground. Example: "They knocked down the old building." (ŠŠ½Šø ŃŠ½ŠµŃŠ»Šø ŃŃŠ°ŃŠ¾Šµ Š·Š“Š°Š½ŠøŠµ.) 14. Settle down ā Start living a stable life or calm down. Example: "They want to settle down and have kids." (ŠŠ½Šø Ń
Š¾ŃŃŃ Š¾ŃŃŠµŠæŠµŠ½ŠøŃŃŃŃ Šø Š·Š°Š²ŠµŃŃŠø Š“ŠµŃŠµŠ¹.) 15. Go down ā Decrease or descend. Example: "The price of gas went down." (Š¦ŠµŠ½Š° Š½Š° Š±ŠµŠ½Š·ŠøŠ½ ŃŠ½ŠøŠ·ŠøŠ»Š°ŃŃ.) 16. Come down ā Move from a higher place or become cheaper. Example: "Come down the stairs carefully." (Š”ŠæŃŃŠŗŠ°Š¹ŃŃ ŠæŠ¾ Š»ŠµŃŃŠ½ŠøŃŠµ Š¾ŃŃŠ¾ŃŠ¾Š¶Š½Š¾.) 17. Hold down ā Keep a job or suppress something. Example: "He holds down two jobs." (ŠŠ½ ŃŠ°Š±Š¾ŃŠ°ŠµŃ Š½Š° Š“Š²ŃŃ
ŃŠ°Š±Š¾ŃŠ°Ń
.) 18. Burn down ā Destroy by fire.Covalent Molecules and Compounds Just as an atom is the simplest unit that has the fundamental chemical properties of an element, a molecule is the simplest unit that has the fundamental chemical properties of a covalent compound. Some pure elements exist as covalent molecules. Hydrogen, nitrogen, oxygen, and the halogens occur naturally as the diatomic (ātwo atomsā) molecules H2, N2, O2, F2, Cl2, Br2, and I2 (part (a) in Figure 3.1.1). Similarly, a few pure elements exist as polyatomic (āmany atomsā) molecules, such as elemental phosphorus and sulfur, which occur as P4 and S8 (part (b) in Figure 3.1.1). Each covalent compound is represented by a molecular formula, which gives the atomic symbol for each component element, in a prescribed order, accompanied by a subscript indicating the number of atoms of that element in the molecule. The subscript is written only if the number of atoms is greater than 1. For example, water, with two hydrogen atoms and one oxygen atom per molecule, is written as H2O. Similarly, carbon dioxide, which contains one carbon atom and two oxygen atoms in each molecule, is written as CO2. Covalent compounds that predominantly contain carbon and hydrogen are called organic compounds. The convention for representing the formulas of organic compounds is to write carbon first, followed by hydrogen and then any other elements in alphabetical order (e.g., CH4O is methyl alcohol, a fuel). Compounds that consist primarily of elements other than carbon and hydrogen are called inorganic compounds; they include both covalent and ionic compounds. In inorganic compounds, the component elements are listed beginning with the one farthest to the left in the periodic table, as in CO2 or SF6. Those in the same group are listed beginning with the lower element and working up, as in ClF. By convention, however, when an inorganic compound contains both hydrogen and an element from groups 13ā15, hydrogen is usually listed last in the formula. Examples are ammonia (NH3) and silane (SiH4). Compounds such as water, whose compositions were established long before this convention was adopted, are always written with hydrogen first: Water is always written as H2O, not OH2. The conventions for inorganic acids, such as hydrochloric acid (HCl) and sulfuric acid (H2SO4), are described elswhere. Note! For organic compounds: write C first, then H, and then the other elements in alphabetical order. For molecular inorganic compounds: start with the element at far left in the periodic table; list elements in same group beginning with the lower element and working up. Write the molecular formula of each compound. a. The phosphorus-sulfur compound that is responsible for the ignition of so-called strike anywhere matches has 4 phosphorus atoms and 3 sulfur atoms per molecule. b. Ethyl alcohol, the alcohol of alcoholic beverages, has 1 oxygen atom, 2 carbon atoms, and 6 hydrogen atoms per molecule. c. Freon-11, once widely used in automobile air conditioners and implicated in damage to the ozone layer, has 1 carbon atom, 3 chlorine atoms, and 1 fluorine atom per molecule. Solution: a. ā¢ A The molecule has 4 phosphorus atoms and 3 sulfur atoms. Because the compound does not contain mostly carbon and hydrogen, it is inorganic. ā¢ B Phosphorus is in group 15, and sulfur is in group 16. Because phosphorus is to the left of sulfur, it is written first. ā¢ C Writing the number of each kind of atom as a right-hand subscript gives P4S3 as the molecular formula. b. ā¢ A Ethyl alcohol contains predominantly carbon and hydrogen, so it is an organic compound. ā¢ B The formula for an organic compound is written with the number of carbon atoms first, the number of hydrogen atoms next, and the other atoms in alphabetical order: CHO. ā¢ C Adding subscripts gives the molecular formula C2H6O. c. ā¢ A Freon-11 contains carbon, chlorine, and fluorine. It can be viewed as either an inorganic compound or an organic compound (in which fluorine has replaced hydrogen). The formula for Freon-11 can therefore be written using either of the two conventions. ā¢ B According to the convention for inorganic compounds, carbon is written first because it is farther left in the periodic table. Fluorine and chlorine are in the same group, so they are listed beginning with the lower element and working up: CClF. Adding subscripts gives the molecular formula CCl3F. ā¢ C We obtain the same formula for Freon-11 using the convention for organic compounds. The number of carbon atoms is written first, followed by the number of hydrogen atoms (zero) and then the other elements in alphabetical order, also giving CCl3F. Write the molecular formula for each compound. a. Nitrous oxide, also called ālaughing gas,ā has 2 nitrogen atoms and 1 oxygen atom per molecule. Nitrous oxide is used as a mild anesthetic for minor surgery and as the propellant in cans of whipped cream. b. Sucrose, also known as cane sugar, has 12 carbon atoms, 11 oxygen atoms, and 22 hydrogen atoms. c. Sulfur hexafluoride, a gas used to pressurize āunpressurizedā tennis balls and as a coolant in nuclear reactors, has 6 fluorine atoms and 1 sulfur atom per molecule. Answer: a. N2O b. C12H22O11 c. SF6. Ionic Compounds The substances described in the preceding discussion are composed of molecules that are electrically neutral; that is, the number of positively-charged protons in the nucleus is equal to the number of negatively-charged electrons. In contrast, ions are atoms or assemblies of atoms that have a net electrical charge. Ions that contain fewer electrons than protons have a net positive charge and are called cations. Conversely, ions that contain more electrons than protons have a net negative charge and are called anions. Ionic compounds contain both cations and anions in a ratio that results in no net electrical charge. Note! Ionic compounds contain both cations and anions in a ratio that results in zero electrical charge.An ionic compound that contains only two elements, one present as a cation and one as an anion, is called a binary ionic compound. One example is MgCl2, a coagulant used in the preparation of tofu from soybeans. For binary ionic compounds, the subscripts in the empirical formula can also be obtained by crossing charges: use the absolute value of the charge on one ion as the subscript for the other ion. This method is shown schematically as follows: Crossing charges. One method for obtaining subscripts in the empirical formula is by crossing charges. When crossing charges, it is sometimes necessary to reduce the subscripts to their simplest ratio to write the empirical formula. Consider, for example, the compound formed by Mg2+ and O2ā. Using the absolute values of the charges on the ions as subscripts gives the formula Mg2O2:Polyatomic Ions Polyatomic ions are groups of atoms that bear net electrical charges, although the atoms in a polyatomic ion are held together by the same covalent bonds that hold atoms together in molecules. Just as there are many more kinds of molecules than simple elements, there are many more kinds of polyatomic ions than monatomic ions. Two examples of polyatomic cations are the ammonium (NH4+) and the methylammonium (CH3NH3+) ions. P. The method used to predict the empirical formulas for ionic compounds that contain monatomic ions can also be used for compounds that contain polyatomic ions. The overall charge on the cations must balance the overall charge on the anions in the formula unit. Thus, K+ and NO3ā ions combine in a 1:1 ratio to form KNO3 (potassium nitrate or saltpeter), a major ingredient in black gunpowder. Similarly, Ca2+ and SO42ā form CaSO4 (calcium sulfate), which combines with varying amounts of water to form gypsum and plaster of Paris. The polyatomic ions NH4+ and NO3ā form NH4NO3 (ammonium nitrate), a widely used fertilizer and, in the wrong hands, an explosive. One example of a compound in which the ions have charges of different magnitudes is calcium phosphate, which is composed of Ca2+ and PO43ā ions; it is a major component of bones. The compound is electrically neutral because the ions combine in a ratio of three Ca2+ ions [3(+2) = +6] for every two ions [2(ā3) = ā6], giving an empirical formula of Ca3(PO4)2; the parentheses around PO4 in the empirical formula indicate that it is a polyatomic ion. Writing the formula for calcium phosphate as Ca3P2O8 gives the correct number of each atom in the formula unit, but it obscures the fact that the compound contains readily identifiable PO43ā ions.Summary ā¢ There are two fundamentally different kinds of chemical bonds (covalent and ionic) that cause substances to have very different properties. ā¢ The composition of a compound is represented by an empirical or molecular formula, each consisting of at least one formula unit.Contributors The atoms in chemical compounds are held together by attractive electrostatic interactions known as chemical bonds. Ionic compounds contain positively and negatively charged ions in a ratio that results in an overall charge of zero. The ions are held together in a regular spatial arrangement by electrostatic forces. Most covalent compounds consist of molecules, groups of atoms in which one or more pairs of electrons are shared by at least two atoms to form a covalent bond. The atoms in molecules are held together by the electrostatic attraction between the positively charged nuclei of the bonded atoms and the negatively charged electrons shared by the nuclei. The molecular formula of a covalent compound gives the types and numbers of atoms present. Compounds that contain predominantly carbon and hydrogen are called organic compounds, whereas compounds that consist primarily of elements other than carbon and hydrogen are inorganic compounds. Diatomic molecules contain two atoms, and polyatomic molecules contain more than two. A structural formula indicates the composition and approximate structure and shape of a molecule. Single bonds, double bonds, and triple bonds are covalent bonds in which one, two, and three pairs of electrons, respectively, are shared between two bonded atoms. Atoms or groups of atoms that possess a net electrical charge are called ions; they can have either a positive charge (cations) or a negative charge (anions). Ions can consist of one atom (monatomic ions) or several (polyatomic ions). The charges on monatomic ions of most main group elements can be predicted from the location of the element in the periodic table. Ionic compounds usually form hard crystalline solids with high melting points. Covalent molecular compounds, in contrast, consist of discrete molecules held together by weak intermolecular forces and can be gases, liquids, or solids at room temperature and pressure. An empirical formula gives the relative numbers of atoms of the elements in a compound, reduced to the lowest whole numbers. The formula unit is the absolute grouping represented by the empirical formula of a compound, either ionic or covalent. Empirical formulas are particularly useful for describing the composition of ionic compounds, which do not contain readily identifiable molecules. Some ionic compounds occur as hydrates, which contain specific ratios of loosely bound water molecules called waters of hydration.āThereās No Such Thing as Sound Scienceā by By Christie Aschwanden was a lead science writer for FiveThirtyEight. FiveThirtyEight, Science, Dec. 6, 2017 Science is being turned against itself. For decades, its twin ideals of transparency and rigor have been weaponized by those who disagree with results produced by the scientific method. Under the Trump administration, that fight has ramped up again. In a move ostensibly meant to reduce conflicts of interest, Environmental Protection Agency Administrator Scott Pruitt has removed a number of scientists from advisory panels and replaced some of them with representatives from industries that the agency regulates. Like many in the Trump administration, Pruitt has also cast doubt on the reliability of climate science. For instance, in an interview with CNBC, Pruitt said that āmeasuring with precision human activity on the climate is something very challenging to do.ā Similarly, Trumpās pick to head NASA, an agency that oversees a large portion the nationās climate research, has insisted that research into human influence on climate lacks certainty, and he falsely claimed that āglobal temperatures stopped rising 10 years ago.ā Kathleen Hartnett White, Trumpās nominee to head the White House Council on Environmental Quality, said in a Senate hearing last month that she thinks we āneed to have more precise explanations of the human role and the natural roleā in climate change. The same entreaties crop up again and again: We need to root out conflicts. We need more precise evidence. What makes these arguments so powerful is that they sound quite similar to the points raised by proponents of a very different call for change thatās coming from within science. This other movement strives to produce more robust, reproducible findings. Despite having dissimilar goals, the two forces espouse principles that look surprisingly alike: Science needs to be transparent. Results and methods should be openly shared so that outside researchers can independently reproduce and validate them. The methods used to collect and analyze data should be rigorous and clear, and conclusions must be supported by evidence. These are the arguments underlying an āopen scienceā reform movement that was created, in part, as a response to a āreproducibility crisisā that has struck some fields of science.1 But theyāre also used as talking points by politicians who are working to make it more difficult for the EPA and other federal agencies to use science in their regulatory decision-making, under the guise of basing policy on āsound science.ā Scienceās virtues are being wielded against it. What distinguishes the two calls for transparency is intent: Whereas the āopen scienceā movement aims to make science more reliable, reproducible and robust, proponents of āsound scienceā have historically worked to amplify uncertainty, create doubt and undermine scientific discoveries that threaten their interests. āOur criticisms are founded in a confidence in science,ā said Steven Goodman, co-director of the Meta-Research Innovation Center at Stanford and a proponent of open science. āThatās a fundamental difference ā weāre critiquing science to make it better. Others are critiquing it to devalue the approach itself.ā Calls to base public policy on āsound scienceā seem unassailable if you donāt know the termās history. The phrase was adopted by the tobacco industry in the 1990s to counteract mounting evidence linking secondhand smoke to cancer. A 1992 Environmental Protection Agency report identified secondhand smoke as a human carcinogen, and Philip Morris responded by launching an initiative to promote what it called āsound science.ā In an internal memo, Philip Morris vice president of corporate affairs Ellen Merlo wrote that the program was designed to ādiscredit the EPA report,ā āprevent states and cities, as well as businesses from passing smoking bansā and āproactivelyā pass legislation to help their cause. The sound science tactic exploits a fundamental feature of the scientific process: Science does not produce absolute certainty. Contrary to how itās sometimes represented to the public, science is not a magic wand that turns everything it touches to truth. Instead, itās a process of uncertainty reduction, much like a game of 20 Questions. Any given study can rarely answer more than one question at a time, and each study usually raises a bunch of new questions in the process of answering old ones. āScience is a process rather than an answer,ā said psychologist Alison Ledgerwood of the University of California, Davis. Every answer is provisional and subject to change in the face of new evidence. Itās not entirely correct to say that āthis study proves this fact,ā Ledgerwood said. āWe should be talking instead about how science increases or decreases our confidence in something.ā The tobacco industryās brilliant tactic was to turn this baked-in uncertainty against the scientific enterprise itself. While insisting that they merely wanted to ensure that public policy was based on sound science, tobacco companies defined the term in a way that ensured that no science could ever be sound enough. The only sound science was certain science, which is an impossible standard to achieve. āDoubt is our product,ā wrote one employee of the Brown & Williamson tobacco company in a 1969 internal memo. The note went on to say that doubt āis the best means of competing with the ābody of factāā and āestablishing a controversy.ā These strategies for undermining inconvenient science were so effective that theyāve served as a sort of playbook for industry interests ever since, said Stanford University science historian Robert Proctor. The sound science push is no longer just Philip Morris sowing doubt about the links between cigarettes and cancer. Itās also a 1998 action plan by the American Petroleum Institute, Chevron and Exxon Mobil to āinstall uncertaintyā about the link between greenhouse gas emissions and climate change. Itās industry-funded groupsā late-1990s effort to question the science the EPA was using to set fine-particle-pollution air-quality standards that the industry didnāt want. And then there was the more recent effort by Dow Chemical to insist on more scientific certainty before banning a pesticide that the EPAās scientists had deemed risky to children. Now comes a move by the Trump administrationās EPA to repeal a 2015 rule on wetlands protection by disregarding particular studies. (To name just a few examples.) Doubt merchants arenāt pushing for knowledge, theyāre practicing what Proctor has dubbed āagnogenesisā ā the intentional manufacture of ignorance. This ignorance isnāt simply the absence of knowing something; itās a lack of comprehension deliberately created by agents who donāt want you to know, Proctor said.2 In the hands of doubt-makers, transparency becomes a rhetorical move. āItās really difficult as a scientist or policy maker to make a stand against transparency and openness, because well, who would be against it?ā said Karen Levy, researcher on information science at Cornell University. But at the same time, āyou can couch everything in the language of transparency and it becomes a powerful weapon.ā For instance, when the EPA was preparing to set new limits on particulate pollution in the 1990s, industry groups pushed back against the research and demanded access to primary data (including records that researchers had promised participants would remain confidential) and a reanalysis of the evidence. Their calls succeeded and a new analysis was performed. The reanalysis essentially confirmed the original conclusions, but the process of conducting it delayed the implementation of regulations and cost researchers time and money. Delay is a time-tested strategy. āGridlock is the greatest friend a global warming skeptic has,ā said Marc Morano, a prominent critic of global warming research and the executive director of ClimateDepot.com, in the documentary āMerchants of Doubtā (based on the book by the same name). Moranoās site is a project of the Committee for a Constructive Tomorrow, which has received funding from the oil and gas industry. āWeāre the negative force. Weāre just trying to stop stuff.ā Some of these ploys are getting a fresh boost from Congress. The Data Quality Act (also known as the Information Quality Act) was reportedly written by an industry lobbyist and quietly passed as part of an appropriations bill in 2000. The rule mandates that federal agencies ensure the āquality, objectivity, utility, and integrity of informationā that they disseminate, though it does little to define what these terms mean. The law also provides a mechanism for citizens and groups to challenge information that they deem inaccurate, including science that they disagree with. āIt was passed in this very quiet way with no explicit debate about it ā that should tell you a lot about the real goals,ā Levy said. But whatās most telling about the Data Quality Act is how itās been used, Levy said. A 2004 Washington Post analysis found that in the 20 months following its implementation, the act was repeatedly used by industry groups to push back against proposed regulations and bog down the decision-making process. Instead of deploying transparency as a fundamental principle that applies to all science, these interests have used transparency as a weapon to attack very particular findings that they would like to eradicate. Now Congress is considering another way to legislate how science is used. The Honest Act, a bill sponsored by Rep. Lamar Smith of Texas,3 is another example of what Levy calls a āTrojan horseā law that uses the language of transparency as a cover to achieve other political goals. Smithās legislation would severely limit the kind of evidence the EPA could use for decision-making. Only studies whose raw data and computer codes were publicly available would be allowed for consideration. That might sound perfectly reasonable, and in many cases it is, Goodman said. But sometimes there are good reasons why researchers canāt conform to these rules, like when the data contains confidential or sensitive medical information.4 Critics, which include more than a dozen scientific organizations, argue that, in practice, the rules would prevent many studies from being considered in EPA reviews.5 It might seem like an easy task to sort good science from bad, but in reality itās not so simple. āThereās a misplaced idea that we can definitively distinguish the good from the not-good science, but itās all a matter of degree,ā said Brian Nosek, executive director of the Center for Open Science. āThere is no perfect study.ā Requiring regulators to wait until they have (nonexistent) perfect evidence is essentially āa way of saying, āWe donāt want to use evidence for our decision-making,āā Nosek said. Most scientific controversies arenāt about science at all, and once the sides are drawn, more data is unlikely to bring opponents into agreement. Michael Carolan, who researches the sociology of technology and scientific knowledge at Colorado State University, wrote in a 2008 paper about why objective knowledge is not enough to resolve environmental controversies. āWhile these controversies may appear on the surface to rest on disputed questions of fact, beneath often reside differing positions of value; values that can give shape to differing understandings of what āthe factsā are.ā Whatās needed in these cases isnāt more or better science, but mechanisms to bring those hidden values to the forefront of the discussion so that they can be debated transparently. āAs long as we continue down this unabashedly naive road about what science is, and what it is capable of doing, we will continue to fail to reach any sort of meaningful consensus on these matters,ā Carolan writes. The dispute over tobacco was never about the science of cigarettesā link to cancer. It was about whether companies have the right to sell dangerous products and, if so, what obligations they have to the consumers who purchased them. Similarly, the debate over climate change isnāt about whether our planet is heating, but about how much responsibility each country and person bears for stopping it. While researching her book āMerchants of Doubt,ā science historian Naomi Oreskes found that some of the same people who were defending the tobacco industry as scientific experts were also receiving industry money to deny the role of human activity in global warming. What these issues had in common, she realized, was that they all involved the need for government action. āNone of this is about the science. All of this is a political debate about the role of government,ā she said in the documentary. These controversies are really about values, not scientific facts, and acknowledging that would allow us to have more truthful and productive debates. What would that look like in practice? Instead of cherry-picking evidence to support a particular view (and insisting that the science points to a desired action), the various sides could lay out the values they are using to assess the evidence. For instance, in Europe, many decisions are guided by the precautionary principle ā a system that values caution in the face of uncertainty and says that when the risks are unclear, it should be up to industries to show that their products and processes are not harmful, rather than requiring the government to prove that they are harmful before they can be regulated. By contrast, U.S. agencies tend to wait for strong evidence of harm before issuing regulations. Both approaches have critics, but the difference between them comes down to priorities: Is it better to exercise caution at the risk of burdening companies and perhaps the economy, or is it more important to avoid potential economic downsides even if it means that sometimes a harmful product or industrial process goes unregulated? In other words, under what circumstances do we agree to act on a risk? How certain do we need to be that the risk is real, and how many people would need to be at risk, and how costly is it to reduce that risk? Those are moral questions, not scientific ones, and openly discussing and identifying these kinds of judgment calls would lead to a more honest debate. Science matters, and we need to do it as rigorously as possible. But science canāt tell us how risky is too risky to allow products like cigarettes or potentially harmful pesticides to be sold ā those are value judgements that only humans can make.LastLAST MINUTE FORENSIC SCIENCELast Minute Risk Assessment