Question

Why c.p is greater than c.v?

Answer 1

Answer:

Explanation:

cp-cv=R

therefore cp=R+cv

hence cp is greater

and R is called gas constant

Answer 2

When a gas is heated, it's volume and pressure both change.

Consider 1 mole of an ideal gas contained in a cylinder, fit with a friction less piston.

Let the cylinder to be heated under two conditions :-

1) When volume of gas is kept constant

By placing weights on the piston, the volume of the gas is kept constant.

Heat supplies in this case would increase the internal energy and temperature of the gas and hence the heat is required only for increasing temperature of gas through 1

2) When pressure of the gas is kept constant

In this case, heat supplied to the gas works in two ways :-

(a) To increase the internal energy  of the gas.

(b) Work is also done in pushing the piston in upward direction.

So,

In the second case, more heat is required for increasing the temperature of the gas through 1 ° C.

Hence,

$C_{p} > C_{v}$