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weinbergshaun

- 12

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**Question (see attached diagram):**PV diagram with 7.5 moles of ideal diatomic gas through cycle a, b and c. What is the highest temperature reached by the gas during the cycle? (multiple choice answers 180, 325, 208 and 100 C, i know answer is 208 C but I'm not getting it!) It is a PV diagram with (triangle), pressure is measured in p(PA x 10^4) and volume is V(m^3) The question is on pg 16 at https://www.scribd.com/doc/287176891:

Point a => p = 3 p(PA x 10^4) and v = 0.2 V(m^3)

Point b => p = 5 p(PA x 10^4) and v = 0.6 V(m^3)

Point c => p = 3 p(PA x 10^4) and v = 0.6 V(m^3)

__Attempt at question:__Point a:

p = 3 PA x 10^4 (im keeping this and will use R = 8.31 L.KPA/K.mol I THINK PA x 10^4 = kPA!)

V = 600 Litres (converted cubic metres to litres times by 1000)

n = 7,5 (this is given even though its diatomic, it will remain as 7,5 since its moles and not molar mass?

R = 8.31 L.KPA/K.mol T = ? PV = nRT T = PV/Rn T = 3 x 600/8.31 x 7,5

Using T = nR/PV:

T = 1800/62.32 T = 28.8 Kelvin

If i apply this to all the other points then i get nowhere near the 208 C, so this example above shows that one of my values is wrong (and will be wrong for all other points b and c).

Many thanks for your help!