Question

Water gas is a mixture of

• A. carbon monoxide and oxygen
• B. carbon monoxide and hydrogen
• C. hydrogen and oxygen
• D. hydrogen and nitrogen

Answer 1

Answer: (B)

Water gas is a mixture of carbon monoxide and hydrogen produced from synthesis gas. Synthesis gas is a useful product, but requires careful handling due to its flammability and the risk of carbon monoxide poisoning. The water-gas shift reaction can be used to reduce the carbon monoxide while producing additional hydrogen, resulting in water gas.

Synthesis gas is made by passing steam over a red-hot carbon fuel such as coke:

$H_{2}O+C\to H_2+CO;(\Delta H=+131kJ/mol)$

The reaction is endothermic, so the fuel must be continually re-heated to keep the reaction going. In order to do this, an air stream, which alternates with the vapor stream, is introduced for the combustion of carbon to take place.

$O_2+C\to C{O}_2(\Delta H=-393kJ/mol)$

Theoretically, to make 6 L of water gas, 5 L of air is required.

Or, alternatively, to prevent contamination with nitrogen, energy can be provided by using pure oxygen to burn carbon into carbon monoxide.

$O_2+2C\to 2CO(\Delta H=-221kJ/mol)$

In this case 1 L of oxygen will create 5.3 L of pure water gas.

Hence, the correct option is $\text{B}$