Question

methane and water react to form hydrogen and carbon monoxide, like this:

ch4(g)+h2o(g)→3h2(g)+co(g)

the reaction is endothermic. suppose a mixture of ch4, h2o, h2 and co has come to equilibrium in a closed reaction vessel. predict what change, if any, the perturbations in the table below will cause in the composition of the mixture in the vessel. also decide whether the equilibrium shifts to the right or left.

Explanation:

Step1: Le - Chatelier's principle for endothermic reaction (temperature raised)

For an endothermic reaction \(CH_{4}(g)+H_{2}O(g)\to3H_{2}(g)+CO(g)\), when the temperature is raised, the system will try to absorb the added heat. According to Le - Chatelier's principle, the equilibrium will shift in the direction of the endothermic reaction (to the right). As the reaction shifts to the right, more \(H_{2}O\) is consumed. So, the pressure of \(H_{2}O\) will decrease.

Step2: Le - Chatelier's principle for endothermic reaction (temperature lowered)

When the temperature is lowered for an endothermic reaction, the system will try to compensate for the loss of heat. The equilibrium will shift in the direction of the exothermic reaction (reverse reaction, to the left). As the reaction shifts to the left, more \(CO\) is consumed. So, the pressure of \(CO\) will decrease.

Answer:

perturbation	change in composition	shift in equilibrium
The temperature is lowered	decrease	to the left