Final answer:
When the number of moles of a gas is doubled and the pressure is halved at constant volume, the absolute temperature of the gas remains the same.
Step-by-step explanation:
When the number of moles of a gas is doubled and the pressure is halved at constant volume, the absolute temperature of the gas remains the same. This is because the relationship between pressure and temperature, known as Gay-Lussac's law, states that pressure is directly proportional to temperature. Therefore, if the pressure is halved, the temperature will also be halved to maintain the same proportionality.