Equilibria (triple) quiz

1. What will happen to the yield of C when the pressure is decreased? Give a reason for your prediction. A (g) + B (g) ⇋ C (g) (+∆H)

Increases, because there are more molecules on the right hand side

Decreases, because there are more molecules on the right hand side

Increases, because there are more molecules on the left hand side

Decreases, because there are more molecules on the left hand side

Question 1 of 15

2. In a calorimetry experiment to investigate the heat energy released by the combustion of ethanol, why should the water in the calorimeter be stirred?

To prevent the water from evaporating

To ensure the heat energy is mixed evenly throughout all the water

To ensure the container does not get too hot

To allow the heat to spread evenly through the copper container

Question 2 of 15

3. 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 3 of 15

4. Gas particles move at a speed of several hundred metres per second at room temperature. Explain why gases take several minutes to diffuse across a room

Gas particles collide with air particles and move in random directions

Gas particles are lazy and do not want to reach the other side of the room

Gas particles collide with air particles and move in only one direction

Gas particles travel very slowly

Question 4 of 15

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

At constant pressure

In a sealed container

In a cool environment (below 0⁰C)

In a warm environment (above 0⁰C)

Question 5 of 15

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

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

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

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 reduces the activation energy, and is not used up

Question 6 of 15

7. Explain the effects of increasing the concentration of solutions on the rate of a reaction in terms of particle collision theory

1) more particles in same space 2) less frequent collisions 3) increase rate of reaction

1) more particles in same space 2) more frequent collisions 3) increase rate of reaction

1) more particles in same space 2) more frequent collisions 3) decrease rate of reaction

1) more particles in same space 2) less frequent collisions 3) decrease rate of reaction

Question 7 of 15

8. Write a chemical equation for the reaction between hydrogen chloride and ammonia

2NH₃ + 2HCl ⇌ 2NH₃Cl + H₂

NH₃ + HCl ⇌ NH₄Cl + H₂O

2NH₄ + 2HCl ⇌ 2NH₄Cl + H₂

NH₃ + HCl ⇌ NH₄Cl

Question 8 of 15

9. State two features of a reaction that is in dynamic equilibrium

1) The rate of the forward reaction is equal to the rate of the backward reaction. 2) There is no overall change in concentrations.

1) The equilibrium is on the right hand side producing a greater concentration of product than reactant. 2) The rate of the forward reaction is equal to the rate of the backward reaction

1) The concentrations of products and reactants are equal. 2) the rate of the forward reaction is equal to the rate of the backward reaction

1) The rate of the forward reaction is greater than the rate of the backward reaction. 2) there is no overall change in concentrations

Question 9 of 15

10. State the expression for calculating % yield.

% yield = (theroretical amount of products/actual amount of products)

% yield = (actual amount of products/theoretical amount of products) x 100

% yield = (theroretical amount of products/actual amount of products) x 100

% yield = (actual amount of products/theoretical amount of products)

Question 10 of 15

11. What does this diagram represent?

Energy level diagram for an endothermic reaction

Reaction profile for an exothermic reaction

Energy level diagram for an exothermic reaction

Reaction profile for an endothermic reaction

Question 11 of 15

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

Cream

White

Blue

Purple

Question 12 of 15

13. What is meant by the term activation energy?

The maximum energy of the final product for it to be stable

The minimum energy that the particles in collision must have if a reaction is going to occur

The energy provided by the catalyst to allow a reaction to proceed

The energy released by the reaction

Question 13 of 15

14. What type of substance speeds up a chemical reaction but is chemically unchanged at the end of the reaction?

Ore

Solute

Catalyst

Reagent

Question 14 of 15

15. What does the symbol ⇌ mean?

Reversible reaction

Equal amounts of reactants and products

A reaction that requires a catalyst

Variable oxidation state

Question 15 of 15

Equilibria (triple) quiz

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