Equilibria (triple) quiz

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

Increases because the backward reaction is endothermic

Decreases because the backward reaction is exothermic

Decreases because the forward reaction is endothermic

Increases because the forward reaction is exothermic

Question 1 of 15

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

In a warm environment (above 0⁰C)

At constant pressure

In a sealed container

In a cool environment (below 0⁰C)

Question 2 of 15

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

Catalyst

Solute

Ore

Reagent

Question 3 of 15

4. State the expression for calculating % yield.

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

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

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

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

Question 4 of 15

5. What does the symbol ΔH mean

exothermic

specific heat capacity

heat energy

enthalpy (energy) change

Question 5 of 15

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

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

Different equipment produces different results. 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

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

Question 6 of 15

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

2NH₄ + 2HCl ⇌ 2NH₄Cl + H₂

NH₃ + HCl ⇌ NH₄Cl

NH₃ + HCl ⇌ NH₄Cl + H₂O

2NH₃ + 2HCl ⇌ 2NH₃Cl + H₂

Question 7 of 15

8. What colour is hydrated copper (II) sulfate?

Purple

Blue

White

Cream

Question 8 of 15

9. What does this symbol represent?

Dynamic equilibrium

Rate of forward reaction equals rate of backwards reaction

Reversible reaction

Yield of reaction is the same both ways

Question 9 of 15

10. 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 10 of 15

11. 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 only one direction

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 random directions

Gas particles travel very slowly

Question 11 of 15

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

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 reduces the activation energy, and is not used up

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

Question 12 of 15

13. 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 forwards reaction is greater than 50%

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

Question 13 of 15

14. What is meant by the term endothermic?

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

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

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 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

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

Question 15 of 15

Equilibria (triple) quiz

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