NESA Chemistry Conducting Investigations
1 sample question with marking guides and sample answers · Avg. score: 86.7%
Phosgene is used in industry as a starting material to synthesise useful polymers. Phosgene () is a gas at room temperature and is highly toxic.
Justify a suitable precaution when using phosgene.
Reveal Answer
Phosgene is dangerous to the environment because it is toxic. Therefore, it is important to ensure it does not leak from the reaction vessel, which requires constant monitoring.
| Descriptor | Marks |
|---|---|
Justifies a named precaution | 2 |
Provides any relevant information | 1 |
None of the above | 0 |
Phosgene is synthesised by the reaction of carbon monoxide (CO) and chlorine () in the gas phase.
Explain why an excess of carbon monoxide and a catalyst are used in the industrial synthesis of phosgene.
Reveal Answer
The use of a catalyst saves time and money because it increases the rate of reaction by lowering the activation energy. The use of a large excess of CO causes the equilibrium to shift to the products side, therefore improving the yield of phosgene.
| Descriptor | Marks |
|---|---|
Explains the use of a catalyst AND Explains the use of a large excess of CO | 3 |
Describes how BOTH features affect the reaction but does NOT link cause and effect OR Explains how one feature affects the reaction | 2 |
Provides any relevant information | 1 |
None of the above | 0 |