according to the first reaction, 2moles of copper(II) carbonate produces 2.5moles of gas. The second equation tells you that 1 mole of copper(II) carbonate produces 1mole of gas.
It seems that you have 2 conflicting equations because both involve CuCO3. First, decide if the condition of the reaction favours the first or second equation. If both happens, what is the extent of reaction for each of them? What factors account for individual extent of reaction?