# Change in temperature between the initial and final state of the gas?

#### mattmannmf

Not sure what im doing wrong

What is the change in temperature between the initial and final state of the gas?

A) A monatomic, ideal gas is in a sealed container (the number of gas molecules is always constant: n = 2 moles); the initial pressure is Pi = 1.01 x 10^5 Pa and the initial volume is Vi = 0.0224 m3.

First, the volume of the gas is decreased at a constant pressure (at Pi = 1.01 x 10^5 Pa) to a final volume of Vf = 0.0155 m3.
Second, the pressure of the gas is increased at a constant volume (at Vf = 0.0155 m3) to a final pressure of Pf = 1.35 x 10^5 Pa.

R=8.13 (given)

Initial Temp= (1.01x10^5*.0224)/(8.13*2)= 136 (this is correct)
Final temp= (1.35x10^5*.0155)/(8.13*2)= 128.7

Delta T= Tf-Ti....128.7-136= -7.3 (which isn't correct)

what am i doing wrong...

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#### mattmannmf

It must be the final temp that im doing wrong

#### iamthegelo

Try,

(Pi*Vi)/Ti = (Pf*Vf)/Tf

solve for Tf

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