IB Chemistry SL 1.1 Measuring Enthalpy Changes Questions

The increased concentration of carbon dioxide in the atmosphere is thought to result from the increased combustion of fossil fuels such as petroleum.

Outline why the energy available from an engine will be less than these theoretical values.

Chlorine occurs in Group 7, the halogens.

Chloroethene, $\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}$, the monomer used in the polymerization reaction in the manufacture of the polymer poly(chloroethene), PVC, can be synthesized in the following two-stage reaction pathway.

Stage 1: $\quad \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{g})$

Stage 2: $\quad \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{g}) \rightarrow \mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}(\mathrm{g})+\mathrm{HCl}(\mathrm{g})$

State whether the reaction given in stage 1 is exothermic or endothermic.

Phenylethene (styrene) is produced from ethylbenzene in a gas-phase equilibrium.

The forward reaction is endothermic, uses iron(III) oxide as a catalyst, and takes place at 900 K .

Sketch the energy profile for the reaction, both with and without the catalyst, labelling $\Delta H$ and the activation energies.