Three moles of a certain diatomic molecular gas are heated at constant pressure

Question

Three moles of a certain diatomic molecular
gas are heated at constant pressure from
300 K to 400 K.
The heat capacity of this gas under constant
pressure is 28.8 J/mol · K. The universal
gas constant is 8.31451 J/mol · K.
Calculate the heat transferred to the gas.
Answer in units of J.
002
Calculate the increase in its internal energy.
Answer in units of J.
003
Calculate the work done by the gas. Answer
in units of J.

001: 8640 J
002: 6145.65 J
003: 2494.35 J

I tried to find the internal energy first using (3/2)*3*8.314*300for u1 and the same but 400 for u2 then subtracted u2 from u1 andgot 3741.53 which is not right and I'm not sure how to get to theright answer and i think i need u and w so i can do U-W to findHeat transfer. im just not sure where to go any help would beappreciated.

Explanation / Answer

(a) Q = ncp T    Q = 3*28.8*(400-300) =8640J
(b) Eint = ncv T = n( cp-R) T = 3 ( 28.8 - 8.314) (100K)             = 6145.65 J
(c) From first law of thermodynamics      Q= Eint + W    therefore W =  Q -Eint  = 8640 - 6145.65 = 2494.35J

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