Question 1

In a chemical reaction, if 5 grams of reactants produce 5 grams of products, which statement best describes this observation?

Accepted Answer

The law of conservation of mass states that mass is neither created nor destroyed.

Answer

Mass is lost during a reaction.

Answer

Mass changes form but is not conserved.

Answer

Mass can be created in chemical reactions.

Question 2

The chemical equation for photosynthesis is represented as

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

. How does this equation demonstrate the law of conservation of mass?

Accepted Answer

The number of atoms for each element is the same on both the reactant and product sides.

Answer

The energy absorbed from sunlight is converted into new carbon atoms within the glucose molecule.

Answer

The total number of molecules on the reactant side is equal to the number on the product side.

Answer

The physical state of the reactants is identical to the physical state of the products.

Question 3

A student mixes 10 grams of vinegar with 5 grams of baking soda in a sealed container. After the reaction finishes, a new gas and a liquid solution are formed. What is the total mass of the contents inside the sealed container?

Accepted Answer

The total mass will remain 15 grams because atoms are only rearranged.

Answer

The total mass will be 0 grams because the reactants were fully consumed.

Answer

The total mass will be more than 15 grams because a new substance formed.

Answer

The total mass will be less than 15 grams because a gas was produced.

Question 4

A student is modeling the conservation of mass in the reaction

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

. Which statement correctly relates the rearrangement of atoms to the total mass of the system?

Accepted Answer

The four hydrogen atoms and two oxygen atoms are rearranged into water molecules, keeping the total mass constant.

Answer

The atoms of the reactants are destroyed to create new elements in the products, causing a slight decrease in total mass.

Answer

The number of oxygen atoms doubles during the reaction to balance the hydrogen atoms, resulting in an increase in mass.

Answer

The chemical bonds between the atoms are converted into new matter, ensuring that the products weigh more than the reactants.

Question 5

In the chemical equation for cellular respiration,

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

, how does the arrangement of oxygen atoms support the law of conservation of mass?

Accepted Answer

The 18 oxygen atoms in the reactants are rearranged into the products so that 18 oxygen atoms remain.

Answer

The oxygen atoms combine with hydrogen to increase the total mass of the products compared to the reactants.

Answer

The 6 oxygen molecules are destroyed during the reaction to allow for the creation of new carbon atoms.

Answer

The 12 oxygen atoms in the glucose molecule are converted into energy to power the chemical reaction.

Question 6

A student observes that when a piece of wood burns in an open fireplace, the resulting pile of ashes has much less mass than the original wood. How does this observation relate to the law of conservation of mass?

Accepted Answer

Mass is conserved because the missing mass was released into the air as carbon dioxide gas and water vapor.

Answer

Mass is gained during the reaction because the oxygen from the air adds more atoms than were originally in the wood.

Answer

Mass is not conserved in combustion reactions because the high heat destroys some of the atoms in the wood.

Answer

Mass is only conserved in liquid reactions, while solid to gas reactions result in a permanent loss of total matter.

Question 7

A student models the law of conservation of mass using the equation for the formation of rust:

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

. Which statement correctly explains the relationship between the atoms and the total mass?

Accepted Answer

The four iron atoms and six oxygen atoms are rearranged into a new compound without any change in the total number of atoms or mass.

Answer

The iron atoms are destroyed to release energy, which is then used to bond the remaining oxygen atoms into a heavier solid product.

Answer

The total mass decreases because the gaseous oxygen atoms are condensed into a smaller volume when they react with the solid iron.

Answer

The total mass increases because the number of molecules decreases from seven on the reactant side to only two on the product side.

Question 8

In the chemical equation for the decomposition of water,

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

, why is the total mass of the reactants always equal to the total mass of the products?

Accepted Answer

The same number and types of atoms are present before and after the reaction, but they are rearranged into different molecules.

Answer

The total number of molecules must remain the same throughout the reaction to ensure that the mass does not fluctuate.

Answer

Liquid water has the same density as hydrogen and oxygen gas, which maintains the overall balance of the entire system.

Answer

The energy required to break the bonds of the water molecules adds the exact amount of mass needed to create oxygen gas.

Question 9

A student uses the chemical equation for the formation of methane,

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

, to model conservation of mass. If the mass of the carbon is 12 grams and the mass of the hydrogen is 4 grams, which statement accurately describes the product?

Accepted Answer

The mass of the methane produced will be 16 grams because the one carbon atom and four hydrogen atoms are simply rearranged.

Answer

The mass of the methane produced will be 32 grams because the number of molecules doubles when the carbon and hydrogen combine.

Answer

The mass of the methane produced will be 12 grams because the hydrogen gas is lighter than the carbon and does not add mass.

Answer

The mass of the methane produced will be 8 grams because half of the atoms are lost as thermal energy during the bonding process.

Question 10

Which of the following best explains how the chemical equation for photosynthesis,

6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

, demonstrates that mass is conserved?

Accepted Answer

The total number of carbon, hydrogen, and oxygen atoms in the reactants is equal to the total number of carbon, hydrogen, and oxygen atoms in the products.

Answer

The mass of the sunlight absorbed by the plant is equal to the mass of the glucose sugar that is produced by the chemical reaction.

Answer

The total number of molecules on the left side of the equation is equal to the total number of molecules on the right side of the equation.

Answer

The state of matter of the reactants is converted from a gas to a solid to ensure that the gravitational pull on the atoms remains constant.

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