Calculate the entropy increment (delta S) at an isochoric transition of 12 g of helium from pressure

Calculate the entropy increment (delta S) at an isochoric transition of 12 g of helium from pressure p1 = 100 kPa to pressure p2 = 80 kPa.

We convert the units of measurement into the CI system and write down what is given and what needs to be found: m = 12 * 10 ^ -3 kg p1 = 10 ^ 5 Pa p2 = 0.8 * 10 ^ 5 Pa M = 4 * 10 ^ -3 kg / mol ΔS =?

The entropy formula for an ideal gas in an isochoric process is as follows:

ΔS = (m / M) * Сv * ㏑ (T2 / T1) = (i / 2) * (m / M) * R * ㏑ (T2 / T1);

i = 3 (Helium is a monatomic gas.)

p1 / T1 = p2 / T2 (The process is isochoric.)

T2 / T1 = p2 / p1

ΔS = (3/2) * (12 * 10 ^ -3 / 4 * 10 ^ -3) * 8.31 * ㏑ (10 ^ 5 / 0.8 * 10 ^ 5) = 41 J / K