Question

When hydrogen molecules decomposed into its atoms which conditions gives maximum yields of $H$ atoms?

• A. High temperature and low pressure
• B. Low temperature and high pressure
• C. High temperature and high pressure
• D. Low temperature and low pressure

Answer 1

Answer: (A)

High temperature and low pressure

Answer 2

$\underset{\text{hydrogen molecule}}{H_2} {->[\text{Electric arc}][2000^{\circ}]} \underset{\text{atomic hydrogen}}{2H} - 104.5\,kcal$ The reaction is endothermic. For endothermic reaction increase in temperature shift the equilibrium in forward direction. To proceed forward the pressure must be low because for the above reaction, increase of pressure will favoured backward reaction. So, tor maximum yield the conditions are high temperature and low pressure.