A cylinder of fixed capacity of 44 . 8 litres contains helium gas at standard temperature and pressure. The amount of heat needed to raise the temperature of gas in the cylinder by 20 . 0 ° C will be

Question

A cylinder of fixed capacity of 44 . 8 litres contains helium gas at standard temperature and pressure. The amount of heat needed to raise the temperature of gas in the cylinder by 20 . 0 ° C will be (Given gas constant R = 8 . 3 J K - 1 mol - 1 )

TestHub · Accepted Answer

At STP volume occupied by one mole of a gas is $22.4 L$ . Therefore, number of moles are, $n = \frac{44.8}{22.4} = 2 mol$ .

The process is isochoric process as the volume of the cylinder remains fixed and helium is a monatomic gas. Therefore, amount of heat needed will be,

$Q = n Cv Δ T = (2) (\frac{3}{2} R) (20) = 3 \times 8.3 \times 20 = 498 J$

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