Answer:

Water gas, also known as synthesis gas or syngas, is a mixture of carbon monoxide (CO) and hydrogen gas (H2). It is commonly used as a fuel and as a starting material for the production of various chemicals. In the given options, the correct method for the production of water gas is passing steam through a red hot coke bed.

Explanation:

Water gas is produced by a process called steam reforming, which involves the reaction of steam with a carbonaceous material, such as coke. This process can be explained in the following steps:

1. Preparation of coke: Coke is a carbonaceous material that is obtained by heating coal in the absence of air. It is a porous substance that provides a large surface area for the reaction to occur.

2. Heating the coke: The coke is then heated to a high temperature, typically around 1000-1100°C, in a reaction vessel or furnace. This is done in the absence of oxygen to prevent the complete combustion of the coke.

3. Passing steam through the coke bed: Steam, which is water in the gaseous state, is then passed through the red-hot coke bed. The high temperature of the coke promotes the reaction between steam and carbon to produce carbon monoxide and hydrogen gas.

The overall reaction can be represented as follows:
C(s) + H2O(g) → CO(g) + H2(g)

In this reaction, carbon from the coke reacts with steam to produce carbon monoxide and hydrogen gas. These gases can be separated and used for various purposes, such as fuel for heating and as starting materials for the production of chemicals.

It is important to note that the other options listed in the question do not describe the correct method for the production of water gas. Saturating hydrogen with moisture does not involve the use of coke or the reaction with steam. Mixing oxygen and hydrogen in the ratio of 1:2 would result in the production of water (H2O) and not water gas. Heating a mixture of CO2 and CH4 in petroleum refineries does not lead to the production of water gas either.

Therefore, the correct answer is option 'A' - Passing steam through a red hot coke bed.