In adiabatic compression, the change in internal energy of a gas is equal to the work done on it, assuming no heat exchange occurs. If the calculated change in internal energy is 1600J, then the work done on the gas is also 1600J. This relationship is derived from the first law of thermodynamics, which states that the change in internal energy equals the heat added to the system minus the work done by the system. Since there is no heat transfer in adiabatic processes, all the work done contributes to the change in internal energy. Therefore, the work done on the gas is indeed 1600J.