(adsbygoogle = window.adsbygoogle || []).push({}); Please Help! Thermodynamics, the ideal gas equation and temperature change

Hi all! I'm new here! I hope my question gets answered because I'm really confused.

1. The problem statement, all variables and given/known data

An amount of 0.18 mol of an ideal gas is held in an insulated cylinder fitted with a piston.

Atmospheric pressure is 1.0 x 10^5 Pa

The volume of the gas is suddenly increased from 1.8 x 10^3 cm3 to 2.1 x 10^3 cm3.

For the expansion of the gas,

(i) calculate the work done by the gas and hence show that the internal energy changes by 30J

(ii)determine the temperature change of the gas and state whether the change is an increase or a decrease

2. Relevant equations

Δu = q + w

pV=nRT?

3. The attempt at a solution

(i) work done by gas= pressure xΔV

So, work done by gas = 30J

Therefore, Δu = -30J

Part (ii) is the problem here

(ii) 3/2 x nRΔT = Δu

So, ΔT = (30x2)/(3x0.18x8.31) = 13.4 K (decrease) ?

However, when using pV=nRT and re-arranging it such that ΔT=(pΔV)/(nR), the

answer is different and it is an increase

Thanks in advance! Any help is much appreciated!

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# Homework Help: Thermodynamics, the ideal gas equation and temperature change

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