Physical Chemistry

The reaction below shows the thermal decomposition of calcium carbonate, which is carried out in a sealed container:

Explain what is meant by a 'sealed container' in the context of this reversible reaction. [2]

(i) State whether the decomposition of calcium carbonate is an exothermic or endothermic process. Give a reason for your answer, including a statement about bond making or breaking. [2]

(ii) The following bond energies can be used to estimate the enthalpy change (ΔH) for the reaction:

The reaction is: Assume that 1 mole of calcium carbonate decomposes. Use the bond energies above to estimate the enthalpy change (ΔH) for the decomposition of calcium carbonate. Show your working. [3]

State and explain what would happen to the position of equilibrium if some carbon dioxide is removed from the sealed container once equilibrium is established. [2]

Write a balanced chemical equation (using state symbols) for the thermal decomposition of ammonium chloride.

Explain, in terms of energy change and temperature, whether this decomposition is endothermic or exothermic. Include what you would expect to observe if touching the outside of the test tube during the reaction.

The student seals the test tube and heats it until no more solid disappears. After some time, the temperature is kept constant. Explain, in terms of reversible reactions and dynamic equilibrium, what happens inside the sealed test tube.

List all the substances present in the reaction mixture at equilibrium in the sealed test tube, and explain your answer.

If the student lowers the temperature of the sealed test tube while it is at equilibrium, predict how the position of equilibrium will shift and what visible change, if any, the student might observe. Explain your answer.