Question

The work done in heating one mole of an
ideal gas at constant pressure from 15°C to
25°C is
1) +19.87 cal
2)-198.7 cal
3) +198.7 ca 1
4)-19.87 cal


please give reply in step by step explanation​

Answer 1

Answer:

1) +19.87 cal

Explanation:

W = PV = nRT

= (1 mol.)(1.987 cal/K-mol)(△T)

= (1.987 cal/K)(298K - 288K)

= (1.987 cal/K)(10K)

= 19.87 cal.

In Calories unit, R =1.987 cal/K-mol.

As for the positive sign, consider this explanation.

Let the gas be system and everything else is surroundings. Now, We have to do work in order to increase the temperature. So, system's temprature increased and when work is done on the system, we consider that work to be positive. Thats is the sign convention. If Temprature of the system happens to decrease, it means it loses its heat i.e. work. That work is taken to be negative.