Equilibria (triple) quiz

1. What does this symbol represent?

Reversible reaction

Rate of forward reaction equals rate of backwards reaction

Yield of reaction is the same both ways

Dynamic equilibrium

Question 1 of 15

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

Gas diffuses slower because the particles have less energy

Gas diffuses quicker because there is less in its way

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

Gas diffuses quicker because particles have more energy.

Question 2 of 15

3. 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 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

Question 3 of 15

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

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

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

Question 4 of 15

5. 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?

0.56 %

0.857 %

56 %

85.7 %

Question 5 of 15

6. In a sealed container, a reversible reaction can reach a state of ______________________________

Dynamic equilibrium

Static equilibrium

Constant equilibrium

Variable equilibrium

Question 6 of 15

7. What is meant by the term exothermic?

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

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

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

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

Question 7 of 15

8. What does this diagram represent?

Reaction profile for an endothermic reaction

Reaction profile for an exothermic reaction

Energy level diagram for an endothermic reaction

Energy level diagram for an exothermic reaction

Question 8 of 15

9. What will happen to the equilibrium position when we increase pressure ? Give a reason for your prediction. A (g) + B (g) ⇋ C (g) + D (g) (+∆H)

Equilibrium will move to the right because there are more molecules on the right hand side

Equilibrium will move to the left because there are fewer molecules on the left hand side

Equilibrium will not shift in position, because there are the same number of molecules on each side

Equilibrium will move to the left because there are more molecules on the left hand side

Question 9 of 15

10. 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 speeds up a chemical reaction but is used up as the reaction proceeds

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

Question 10 of 15

11. 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 11 of 15

12. Describe the chemical test for water

Find the boiling point. If it is 100 ⁰C water is present

Find the melting point. If it is 0 ⁰C then water is present

Add it to anhydrous potassium permanganate which will turn from white to purple if water is present

Add it to anhydrous copper(II) sulfate which will change from white to blue if water is present

Question 12 of 15

13. With how much energy must two particles collide for a reaction to occur?

The particles must collide with an energy less than the activation energy

The particles must collide with an energy greater than the activation energy

The particles must collide with an energy greater than or equal to the activation energy

The particles must collide with an energy equal to the activation energy

Question 13 of 15

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

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

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

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

Question 14 of 15

15. Explain the effects of increasing the temperature on the rate of a reaction in terms of particle collision theory

1) particles have less kinetic energy 2) less frequent collisions 3) and a lower proportion of the collisions which occur have greater or equal to the activitation energy 4) increase rate of reaction

1) particles have more kinetic energy 2) more frequent collisions 3) and a higher proportion of the collisions which occur have greater or equal to the activation energy 4) increase rate of reaction

1) particles have less kinetic energy 2) less frequent collisions 3) and a lower proportion of the collisions which occur have greater or equal to the activitation energy 4) decrease rate of reaction

1) particles have more kinetic energy 2) more frequent collisions 3) and a lower proportion of the collisions which occur have greater or equal to the activitation energy 4) increase rate of reaction

Question 15 of 15

Equilibria (triple) quiz

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