Reversible reactions and equilibrium — final check

1. identify

Which result shows that a liquid contains water?

Circle one answer.

• Cobalt chloride paper turns from pink to blue
• Anhydrous copper(II) sulfate turns from white to blue
• Blue cobalt chloride paper stays blue
• Copper(II) sulfate turns from blue to white

2. explain / describe

A pupil adds a few drops of a clear liquid to white anhydrous copper(II) sulfate, and it turns blue. They write: "The liquid is pure water." (a) What does the result show? (b) Explain why the conclusion is not justified, and describe how to test whether the water is pure.

(a) What the result shows

(b) Why not justified, and a test for purity

3. identify

Supplement. Which statement about a dynamic equilibrium is correct?

Circle one answer.

• It can be reached in an open beaker that a gas can escape from
• The forward and reverse reactions go on at the same rate
• The amounts of reactants and products are always equal
• The forward and reverse reactions have both stopped

4. predict / explain

Supplement. Hydrogen is made from methane and steam: CH₄(g) + H₂O(g) ⇌ CO(g) + 3H₂(g). The forward reaction is endothermic. Predict and explain the effect on the yield of hydrogen of (a) a higher temperature, (b) a higher pressure.

(a) Higher temperature

(b) Higher pressure

5. identify

Supplement. Which set of conditions is used in the Haber process?

Circle one answer.

• 250 °C, 20 000 kPa (200 atm), iron catalyst
• 450 °C, 20 000 kPa (200 atm), iron catalyst
• 450 °C, 20 000 kPa (200 atm), no catalyst
• 450 °C, 200 kPa (2 atm), vanadium(V) oxide catalyst

6. state / explain

Supplement. In the Haber process: (a) name the sources of the nitrogen and the hydrogen; (b) explain, in terms of rate and position of equilibrium, why 450 °C is used; (c) give one reason, other than the yield, for not using a higher pressure than 200 atm.

(a) Sources

(b) Why 450 °C

(c) A reason not to raise the pressure