... original volume) The volume change may be due to the temperature change and/or a change in moles Consider the change in temperature Examine the balanced reactions for a possible change in number of moles... balanced reaction for a possible change in number of moles Rearrange the ideal gas law to the appropriate form and solve for the variable that changes Solution: The balanced chemical equation must be... mass that matches the calculated value is methane M= 5.10A Plan: Calculate the number of moles of each gas present and then the mole fraction of each gas The partial pressure of each gas equals