The volume of a fixed amount of gas is doubled, and the absolute temperature is doubled. According to the ideal gas law, how has the pressure of the gas changed?

The ideal gas law is PV = nRT. For a fixed amount of gas, n is constant, so pressure is proportional to temperature divided by volume. Doubling both the absolute temperature and the volume leaves their ratio unchanged: (2T)/(2V) = T/V. Therefore, the pressure has stayed the same.

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