Equilibria (triple) quiz

1. State and explain how increasing temperature affects the diffusion of a gas

Gas diffuses quicker because there is less in its way

Gas diffuses slower because the particles have less energy

Gas diffuses quicker because particles have more energy.

Gas diffuses slower because the particles collide more often with the air

Question 1 of 15

2. One feature of dynamic equilibrium is that there is no overall change in concentrations. What is the other?

The rate of the forward reaction is equal to the rate of the backward reaction

The yield of the backward reaction is greater than 50%

The rate of the forward reaction is greater than the rate of the backward reaction

The yield of the forwards reaction is greater than 50%

Question 2 of 15

3. What is a catalyst?

A substance that speeds up a chemical reaction but is chemically unchanged at the end of the reaction

A substance that helps dissolve insoluble reagents to speed up the rate of reaction

A substance that slows down a chemical reaction but is chemically unchanged at the end of the reaction

A substance that speeds up a chemical reaction but is used up as the reaction proceeds

Question 3 of 15

4. What does the symbol ⇌ mean?

Reversible reaction

Variable oxidation state

A reaction that requires a catalyst

Equal amounts of reactants and products

Question 4 of 15

5. Explain why experimental values of enthalpy change differ from theoretical values

Different equipment produces different results. Not all the reactants are used up

Heat energy is lost to the surroundings. Not all the reactants are used up.

Different equipment produces different results. Heat energy is lost to the surroundings. Not all the reactants are used up

Different equipment produces different results. Heat energy is lost to the surroundings

Question 5 of 15

6. What will happen to the yield of CH₃OH when the pressure is decreased? Give a reason for your prediction. CO(g) + 2H₂(g) ⇋ CH₃OH(g) ΔH = –91 kJ mol⁻1

Increases because there are more molecules on the left hand side

Decreases because there are fewer molecules on the left hand side

Decreases because there are more molecules on the left hand side

Increases because there are fewer molecules on the right hand side

Question 6 of 15

7. For a reversible reaction to reach dynamic equilibria, where must the reaction take place?

In a warm environment (above 0⁰C)

In a cool environment (below 0⁰C)

In a sealed container

At constant pressure

Question 7 of 15

8. What happens if two particles collide with less than the activation energy

The reaction still occurs but very slowly

No reaction

The particles fuse together

The reaction only goes partway

Question 8 of 15

9. Why a catalyst does not affect the position of equilibrium in a reversible reaction?

A catalyst reduces the activation energy, and is not used up

If a reversible reaction is in dynamic equilibrium, a catalyst increases the rate of the forward reaction and the rate of the backward reaction by the same amount, so the position of equilibrium is unaffected

A catalyst has no effect on a forward or backward reactions if it is in dynamic equilibrium

A reaction in dynamic equilibrium already has the lowest possible activation energy

Question 9 of 15

10. Explain the effects of increasing the surface area of a solid on the rate of a reaction in terms of particle collision theory

1) more particles exposed 2) less frequent collisions 3) increase rate of reaction

1) more particles exposed 2) more frequent collisions 3) increase rate of reaction

1) more particles exposed 2) less frequent collisions 3) decrease rate of reaction

1) more particles exposed 2) more frequent collisions 3) decrease rate of reaction

Question 10 of 15

11. What colour is anhydrous copper (II) sulfate?

Blue

White

Purple

Cream

Question 11 of 15

12. What does the symbol ΔH mean

specific heat capacity

exothermic

heat energy

enthalpy (energy) change

Question 12 of 15

13. The addition of water to anhydrous copper sulfate can be used to test for the presence of water. The reaction is reversible. What is the word equation? Describe the colour change.

anhydrous copper sulfate (white) + water ⇌ hydrated copper sulfate (blue)

anhydrous copper sulfate (blue) + water ⇌ hydrous copper sulfate (white)

anhydrous copper sulfate (white) + water ⇌ hydrous copper sulfate (blue)

anhydrous copper sulfate (blue) + water ⇌ hydrated copper sulfate (white)

Question 13 of 15

14. What is meant by the term exothermic?

A reaction in which heat energy is taken in (surroundings get colder)

A reaction which will only be spontaneous at warm temperatures (above 100⁰C)

A reaction in which heat energy is given out (surroundings get hotter)

A reaction which will only be spontaneous at cold temperatures (below 0⁰C)

Question 14 of 15

15. In the thermal decomposition of calcium carbonate, we might expect 50g of calcium carbonate to produce 28g of calcium oxide. If instead only 24g of calcium oxide is produced, what is the percentage yield?

85.7 %

0.56 %

56 %

0.857 %

Question 15 of 15

Equilibria (triple) quiz

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