hw, q 19

[Melissa Rojas]

my hw question is: "A 0.617 mol sample of Ar(g) initially at 298 K and 1.00 atm is held at constant volume while enough heat is applied to raise the temperature of the gas by 12.1 K. Assuming ideal gas behavior, calculate the amount of heat (q) in joules required to affect this temperature change and the total change in internal energy, ΔU. Note that some books use ΔE as the symbol for internal energy instead of ΔU".

my question is: so I calculated the problem, but I got a wrong answer. my feedback was that I did not correctly determined the molar heat capacity of the gas. Ar(g)
is a monatomic gas. what do I do next? like what is the molar heat capacity of Ar ? or how would I find it?

thank you !

[Helen Heath 2B]

My version used a nonlinear molecule, but I think for just the atom, CV,m = 3/2 ×8.3145 Jmol⋅K would give you the correct heat capacity. and then you plug in the numbers you have into the q = n × CV,m ×ΔT equation. Hope that helps!

[Emily Diep 2L]

Hi!

Ar(g) fits in the atoms section for types of gas, so using the table provided we can find that the molar heat capacity at constant volume is (3/2)R, where R is the ideal gas constant. The equation for q=m*C*deltaT, but since we know that Ar(g) is atoms type of gas, the equation becomes q=m*(3/2)R*deltaT. In my problem I was given NO2(g) which is a nonlinear molecule, so the molar heat capacity is 3R, so my equation was q=m*3R*deltaT.

[Melissa Rojas]

thank you sm!