Barry M. answered • 7d

Professor, CalTech Grad; Many Years Tutoring Math, SAT/ACT Prep, Chem

Delta E = n x C x delta T, where n = number of moles, C is the heat capacity, and delta T is the temperature change.

For ideal gases, diatomics have C = 5R/2, and monatomics have C = 3R/2. This is C_{v}, where the volume is constant. When pressure is constant, and volume changes, calculate C_{p} by adding R to each of these values to get 7R/2 and 5R/2, respectively.

n = 1.57 and delta T = 306 - 89 = 217.

Use R = 8.314 J/mol-K and plug in to the Delta E equation above. For large values, as here, you may express the answers in kJ (kilojoules), in which case divide by 1000.