Final answer:
A condenser is placed on top of a reaction to capture and condense any vapor or gases produced. It helps increase the yield, remove impurities, and ensure safety.
Step-by-step explanation:
When carrying out a reaction, a condenser is often placed on top of the reaction to capture and condense any vapor or gases that are produced. This is especially important when the reaction is producing a gas that needs to be collected. The condenser helps to cool and condense the vapor or gas, allowing it to be collected in a separate container.
By condensing the vapor or gas, the condenser helps to increase the yield of the desired product. This is because the condensation process helps to remove impurities and unwanted by-products, leaving behind a purer form of the desired product.
Additionally, the condenser also helps to ensure the safety of the reaction by preventing any potentially hazardous gases or vapors from escaping into the surrounding environment.