Question 1

What factors affect the rate of a reaction?

Accepted Answer

temperature, concentration, pressure (in gases), surface area and catalysts

Answer

temperature, concentration, pressure, surface area and concentration

Question 2

What is a catalyst?

Accepted Answer

A species which increases the rate of reaction by providing an alternative pathway with a lower activation energy but is not used up

Answer

A species which increases the rate of reaction by lowering the activation energy but is not used up

Question 3

define activation energy

Accepted Answer

the minimum energy needed for a reaction to occur

Answer

the maximum energy needed for a reaction to occur

Question 4

define collision theory

Accepted Answer

for particles to react they need E>Ea and they must collide in the correct orientation

Answer

for particles to react they need E

Question 5

how does increasing the pressures of gases increase the rate of reaction?

Accepted Answer

particles are closer together so there are more frequent successful collisions

Answer

increases frequency of collisions and also increases the number of molecules that have energy greater than Ea. More frequent successful collisions

Question 6

why does temperature affect reaction rate?

Accepted Answer

increases frequency of collisions and also increases the number of molecules that have energy greater than Ea. More frequent successful collisions

Answer

particles are closer together so there are more frequent successful collisions

Question 7

Why do all reactions have an activation energy?

Accepted Answer

All reactions require bonds within reactants to break. This is an endothermic process.

Answer

All reactions require bonds within products to break. This is an endothermic process.

Question 8

how does increasing the surface area increase the rate of reaction?

Accepted Answer

particles are closer together so there are more frequent successful collisions

Answer

increases frequency of collisions and also increases the number of molecules that have energy greater than Ea. More frequent successful collisions

Question 9

how does increasing concentration of reactants increase the rate of reaction?

Accepted Answer

particles are closer together so there are more frequent successful collisions

Answer

increases frequency of collisions and also increases the number of molecules that have energy greater than Ea. More frequent successful collisions

Question 10

Increasing the size of a solid...

Accepted Answer

decreases surface area (compared to volume)

Answer

increases surface area (compared to volume)

Question 11

How to work out activation energy from a reaction profile?

Accepted Answer

the difference in energy between the top of curve and reactants

Answer

the difference in energy between the top of curve and products

Question 12

what does Maxwell Boltzmann distribution curve show?

Accepted Answer

the distribution of energies of gas particles vary and make a pattern called the MB distribution

Answer

the distribution of energies of gas particles are the same and make a pattern called the MB distribution

Question 13

what does the area under the curve show?

Accepted Answer

total number of particles

Answer

no molecules have no energy

Answer

the highest point of the curve

Question 14

where is the most probable energy on the curve?

Accepted Answer

the highest point of the curve

Answer

no molecules have no energy

Answer

total number of particles

Answer

to the right of the highest point of the curve

Question 15

where is the mean energy on the curve?

Accepted Answer

slightly to the right of the highest point of the curve

Answer

no molecules have no energy

Answer

the highest point of the curve

Answer

total number of particles

Question 16

why does the curve start at the origin?

Accepted Answer

no molecules have no energy

Answer

the highest point of the curve

Answer

total number of particles

Question 17

what does the presence of a catalyst do to the Maxwell Boltzmann curve?

Accepted Answer

does not change the curve but the position of Ea is shifted to the left - molecules with E>Ea have increased

Answer

does not change the amount of energy the particles have so the distribution is not affected but the curve becomes taller (because more particles)

Answer

shifts to the left with a higher peak to show smaller proportion of molecules with E>Ea

Answer

shifts to the right with a lower peak to show greater proportion of molecules E>Ea

Question 18

what does an increase in temperature do to the Maxwell Boltzmann curve?

Accepted Answer

shifts to the right with a lower peak to show greater proportion of molecules E>Ea

Answer

does not change the amount of energy the particles have so the distribution is not affected but the curve becomes taller (because more particles)

Answer

shifts to the left with a higher peak to show smaller proportion of molecules with E>Ea

Answer

does not change the curve but the position of Ea is shifted to the left - molecules with E>Ea have increased

Question 19

what does a decrease in temperature do to the Maxwell Boltzmann curve?

Accepted Answer

shifts to the left with a higher peak to show smaller proportion of molecules with E>Ea

Answer

does not change the amount of energy the particles have so the distribution is not affected but the curve becomes taller (because more particles)

Answer

shifts to the right with a lower peak to show greater proportion of molecules E>Ea

Answer

does not change the curve but the position of Ea is shifted to the left - molecules with E>Ea have increased

Question 20

what does an increase in concentration/pressure do to the Maxwell Boltzmann curve?

Accepted Answer

does not change the amount of energy the particles have so the distribution is not affected but the curve becomes taller (because more particles)

Answer

shifts to the left with a higher peak to show smaller proportion of molecules with E>Ea

Answer

does not change the curve but the position of Ea is shifted to the left - molecules with E>Ea have increased

Answer

shifts to the right with a lower peak to show greater proportion of molecules E>Ea

Question 21

define transition state

Accepted Answer

a state through which a reaction passes between the reactants and products. It is the state with the highest energy

Answer

a state through which a reaction passes between the reactants and products. It is the state with the lowest energy

Question 22

What does total area under curve represent?

Accepted Answer

B

Answer

D

Answer

C

Answer

A

Question 23

Mean energy....

Accepted Answer

C

Answer

D

Answer

A

Answer

B

Question 24

Which is correct

Accepted Answer

A

Answer

C

Answer

B

Answer

D

Question 25

which letter is most probable energy?

Accepted Answer

B

Answer

D

Answer

C

Answer

A

Question 26

Why does doubling the temperature have a significantly greater effect on the reaction rate than doubling the concentration of a reactant?

Accepted Answer

Doubling the temperature causes many more molecules to have this energy whereas doubling the concentration of a reactant only doubles the number of reactants with this energy.

Answer

Doubling the temperature causes many more molecules to have this energy whereas doubling the concentration of a reactant only halves the number of reactants with this energy.

Question 27

Define homogenous catalyst

Accepted Answer

A catalyst that is in the same phase from the reactants which speeds up the reaction without getting used up (usually a gas/ liquid)

Answer

A catalyst that is in a different phase from the reactants which speeds up the reaction without getting used up (usually a solid)

Question 28

Define heterogenous catalyst

Accepted Answer

A catalyst that is in a different phase from the reactants which speeds up the reaction without getting used up (usually a solid)

Answer

A catalyst that is in the same phase from the reactants which speeds up the reaction without getting used up (usually a liquid)

Question 29

How can you minimise the cost of a heterogenous catalyst?

Accepted Answer

spread the powdered catalyst onto a support medium to maximise the surface area

Answer

spread the powdered catalyst onto a support medium to minimise the surface area

Question 30

State 3 examples of the use of transition metals as heterogenous catalysts

Accepted Answer

V2O5 in the Contact process (manufacture of SO3 for H2SO4), Fe (pea-sized lumps) in the Haber process (manufacture of NH3), Rd/Pt/Pd in catalytic converters

Answer

V2O5 in the Haber process (manufacture of SO3 for H2SO4), Fe (pea-sized lumps) in the Contact process (manufacture of NH3), Rd/Pt/Pd in catalytic converters

Question 31

What is a catalytic converter?

Accepted Answer

A honeycomb structure in the exhaust system of a car coated with platinum and rhodium metals that act as catalysts. The catalysts cause harmful products to react with each other and produce less harmful products e.g. carbon monoxide, hydrocarbons and nitrogen oxides to form nitrogen, carbon dioxide and water.

Answer

A honeycomb structure in the exhaust system of a car coated with potassium and rhodium metals that act as catalysts. The catalysts cause harmful products to react with each other and produce less harmful products e.g. carbon monoxide, hydrocarbons and nitrogen oxides to form nitrogen, carbon dioxide and water.

Question 32

Which catalyst is used in the hydrogenation of vegetable oils?

Accepted Answer

Nickel

Answer

Iron

Question 33

The stages involved when a heterogenous catalyst is used

Accepted Answer

Reactants adsorb onto the catalyst surface and are held in the correct orientation to react, this weakens bonds in the reactants and new bonds are formed and the product desorbs from the surface

Answer

Reactants desorb onto the catalyst surface and are held in the correct orientation to react, this weakens bonds in the reactants and new bonds are formed and the product adsorb from the surface

Question 34

Explain why heterogenous catalysts cannot adsorb too weakly

Accepted Answer

reactants not brought together/no increase in reactant concentration on catalyst surface/ reactants not held long enough for a reaction to occur / reactant bonds not weakened

Answer

reactants cannot move on surface or products not desorbed

Question 35

Explain why heterogenous catalysts cannot adsorb too strongly

Accepted Answer

reactants cannot move on surface or products cannot be desorbed

Answer

reactants not brought together/no increase in reactant concentration on catalyst surface/ reactants not held long enough for a reaction to occur / reactant bonds not weakened

Question 36

Define rate of reaction

Accepted Answer

change in concentration of reactants/products per unit time

Answer

change in volume of reactants/products per unit hour

Question 37

How do you determine rate from a concentration time graph?

Accepted Answer

Draw a tangent and calculate the gradient (difference of y/ difference of x)

Answer

Draw a tangent and calculate the area under the graph

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