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For numbers 18 and 19... initial pressure of 4 atm to 0.8 alm. Assuming gas behaves like an ideal gas, Twenty grams of oxygen gas at 25C expand adiabatically and reversibly from an determine the following: 18. Final temperature (C) of the gas a. -55 b.-65 C. -75 d. -85 19. If expansion was done against a constant external pressure of 1 atm, calculate the work (J) done by the gas. a. 1033 b. 1154 d. 1428 c. 1368