Rates and Equilibrium questions

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Rates and Equilibrium question collection

Review Rates and Equilibrium questions for Chemistry, with correct answers shown and coverage across collision theory; factors affecting rate; catalysts and activation energy.

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Question 1

What is the rate of reaction?
  1. Reactant used or product formed per unit time
  2. Total product formed when the reaction ends
  3. Minimum collision energy needed for reaction
  4. Energy transferred between reaction and surroundings

Question 2

\(40\,\mathrm{cm^3}\) of gas is produced in \(20\,\mathrm{s}\). What is the mean rate?
  1. \(2\,\mathrm{cm^3\,s^{-1}}\)
  2. \(0.5\,\mathrm{cm^3\,s^{-1}}\)
  3. \(20\,\mathrm{cm^3\,s^{-1}}\)
  4. \(800\,\mathrm{cm^3\,s^{-1}}\)

Question 3

Why does increasing temperature usually increase reaction rate?
  1. More particles exceed the activation energy
  2. Particles become heavier
  3. Activation energy increases
  4. There are fewer collisions per second

Question 4

Why does increasing concentration often increase reaction rate?
  1. Particles collide more frequently
  2. Particles move more slowly
  3. Activation energy is removed
  4. Reactant particles become catalysts

Question 5

Why does increasing pressure usually increase the rate of gas reactions?
  1. Gas particles collide more frequently
  2. Gas particles lose kinetic energy
  3. There are fewer gas particles present
  4. Catalysts are affected by pressure

Question 6

Why does powdered calcium carbonate react faster than marble chips of the same mass?
  1. It has a larger surface area
  2. It has a higher activation energy
  3. It contains more calcium carbonate
  4. It forms a different product

Question 7

How does a catalyst change a reaction profile?
  1. Lower peak; unchanged start and end energies
  2. Higher peak; unchanged reactant and product energies
  3. Unchanged peak; lower product energy
  4. Unchanged peak; higher reactant energy

Question 8

Why does reaction rate usually fall as reactants are used up?
  1. Reactant concentration falls, reducing collision frequency
  2. Activation energy rises as products form
  3. Reactant particles become heavier during the reaction
  4. The catalyst is gradually converted into product

Question 9

What makes a reaction reversible?
  1. Its products can react to re-form the reactants
  2. Its reactants can form more than one product
  3. Its products form at different rates
  4. Its catalyst can be removed after the reaction

Question 10

What does dynamic equilibrium mean in a closed system?
  1. Forward and reverse reactions occur at equal rates
  2. Both reactions have stopped
  3. Forward reaction occurs
  4. Amounts of reactants and products must be equal

Question 11

Why is a closed system needed for equilibrium?
  1. So reactants and products cannot escape
  2. So the reaction stops completely
  3. So the catalyst is used up
  4. So products can leave at a steady rate

Question 12

How does increasing reactant concentration affect an equilibrium?
  1. It shifts towards products
  2. It shifts towards reactants
  3. It stays fixed because concentrations are constant
  4. It stops both reactions

Question 13

At equilibrium, what happens when a product is removed?
  1. Equilibrium shifts towards the products
  2. Equilibrium shifts towards the reactants
  3. Both reaction rates become zero
  4. The forward reaction becomes irreversible

Question 14

For an exothermic forward reaction, which shift follows a temperature increase?
  1. Towards reactants, the endothermic direction
  2. Towards products, the exothermic direction
  3. Towards the side with fewer gas molecules
  4. No shift because concentration is unchanged

Question 15

For \(\mathrm{N}_2 + 3\mathrm{H}_2 \rightleftharpoons 2\mathrm{NH}_3\), increasing pressure shifts equilibrium?
  1. Toward NH3 because there are fewer gas molecules on that side
  2. Toward N2 and H2 because pressure breaks NH3
  3. Nowhere because pressure has no effect on gases
  4. Toward the side with more molecules

Question 16

What is the effect of a catalyst on the position of equilibrium?
  1. No change
  2. A shift towards products
  3. A shift towards reactants
  4. Equilibrium is not reached

Question 17

Which graph feature indicates a faster initial rate when plotting gas volume against time?
  1. A steeper initial gradient
  2. A lower final gas volume
  3. A longer time to reach plateau
  4. A flatter initial gradient

Question 18

What is collision theory?
  1. Reactions occur when particles collide with enough energy and correct orientation
  2. Reactions occur when particles are motionless
  3. Ionic particles can react
  4. Collisions always cause reactions regardless of energy

Question 19

For \(\mathrm{H}_2(\mathrm{g})+\mathrm{I}_2(\mathrm{g}) \rightleftharpoons 2\mathrm{HI}(\mathrm{g})\), what does higher pressure do?
  1. No shift; both sides have two gas molecules
  2. Shifts right because two product molecules form
  3. Shifts left because reactants occupy more volume
  4. Shifts towards the endothermic side

Question 20

In a rate experiment, \(12\,\mathrm{g}\) of reactant are used in \(4\,\mathrm{min}\). What is the mean rate in \(\mathrm{g\,min^{-1}}\)?
  1. \(3\,\mathrm{g\,min^{-1}}\)
  2. \(0.33\,\mathrm{g\,min^{-1}}\)
  3. \(8\,\mathrm{g\,min^{-1}}\)
  4. \(48\,\mathrm{g\,min^{-1}}\)

Question 21

What is activation energy?
  1. The minimum energy particles need to react
  2. The energy released by an exothermic reaction
  3. The energy stored in products at equilibrium
  4. The energy transferred to a catalyst

Question 22

What is a successful collision?
  1. A collision with enough energy and suitable orientation
  2. Any contact between particles
  3. A collision at lower temperature
  4. A collision with no energy transfer

Question 23

Why does a catalyst increase rate?
  1. It lowers activation energy
  2. It increases product energy
  3. It is used up in the reaction
  4. It removes reactants

Question 24

At dynamic equilibrium, what happens to reactant and product concentrations?
  1. They remain constant but need not be equal
  2. They become equal and remain constant
  3. They both fall to zero
  4. They alternate between high and low values

Question 25

How does increasing pressure affect an equilibrium with fewer gas molecules on the product side?
  1. It shifts equilibrium towards products
  2. It shifts towards the side with more gas molecules
  3. It has no effect on the equilibrium position
  4. It stops both reactions

Question 26

For an endothermic forward reaction, what does increasing temperature favour?
  1. Products
  2. Reactants
  3. The side with fewer gas molecules
  4. Neither side

Question 27

Why record gas volume at regular intervals in a rate experiment?
  1. To see how reaction rate changes over time
  2. To keep the activation energy constant
  3. To prevent the gas from leaving the apparatus
  4. To make the catalyst reusable

Question 28

How is instantaneous rate found from a quantity-time graph?
  1. Find the gradient of a tangent at that time
  2. Find the gradient from the start to the end
  3. Read the time from the horizontal axis
  4. Read the final height of the plateau

Question 29

Which measurement can track a reaction when a gaseous product escapes?
  1. Decrease in mass over time
  2. Initial mass before the reaction
  3. Final temperature after the reaction
  4. Starting pH before reactants are mixed

Question 30

Why is the Haber process not run at a very low temperature, despite the higher yield?
  1. The reaction rate would be too slow
  2. The equilibrium would shift towards nitrogen and hydrogen
  3. The catalyst would raise the activation energy
  4. The pressure would stop affecting the equilibrium

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Review Rates and Equilibrium questions for Chemistry, with correct answers shown and coverage across collision theory; factors affecting rate; catalysts and activation energy.

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