For the endothermic reaction below, when does le chatelier's principle predict that there will be an increase in the number of moles of co2? caco3(s) ⇄ cao(s) + co2(g)

When there is a decrease in the pressure or an increase in volume. As the container gets bigger, it will want to increase the pressure to get back to equilibrium. For that to happen, it will have to increase the number of gas moles, and since co2 is the only has in that equation, it will increase. 

The correct answer is d