What is the function of water in an experiment where dry hydrogen chloride gas is passed through heated zinc turnings and then the gas produced is bubbled through water and then passed through heated lead (2) oxide
The bubbling through water step is to remove the excess dry HCl gas. Otherwise any HCl gas at that pont will give a competing reaction with the PbO.
In this experiment, water serves multiple functions. Let's break it down step by step to understand its role:
1. Dry Hydrogen Chloride Gas and Heated Zinc Turnings: In the initial stage, dry hydrogen chloride gas is passed through heated zinc turnings. This reaction produces hydrogen gas and zinc chloride. The role of water at this stage is not directly involved.
2. Bubbling through Water: The gas produced in the first step, which is hydrogen gas along with any remaining unreacted hydrogen chloride gas, is then bubbled through water. The purpose of bubbling the gas through water is to wash out any impurities or residual gases.
Hydrogen chloride gas can dissolve in water to form hydrochloric acid. By bubbling the gas through water, any hydrochloric acid that is formed will dissolve, effectively removing it from the gas mixture. This step helps to obtain a purer hydrogen gas sample for the subsequent stages of the experiment.
3. Passing through Heated Lead (II) Oxide: After the gas has been bubbled through water, it is passed through heated lead (II) oxide. This reaction leads to the formation of water as a product. The main purpose here is to exploit the strong oxidizing properties of lead (II) oxide.
The reaction between hydrogen gas and lead (II) oxide produces water vapor, as hydrogen reduces the lead (II) oxide to metallic lead while being oxidized itself. This is known as a redox reaction.
To summarize, water is used in the experiment mainly as a means to purify the gas mixture by dissolving any hydrochloric acid formed and to provide the necessary oxygen source for the subsequent reaction with lead (II) oxide.