# Homework Help: More Thermodynamics

1. Jun 19, 2006

### cukitas2001

ok these last few problems have been driving me up a wall an of course its gotta be something simple im missing.

1)
A) Compute the specific heat capacity at constant volume of nitrogen ($$N_2$$) gas. The molar mass of $$N_2$$ is 28.0grams/mol.

the heat capacity of a diatomic molecule is:
$$C_v =\frac{5}{2} R$$ but i dont think this is what im suppsoed to use? help please

B) You warm 1.10kg of water at a constant volume from 18.0 celsius to 30.5 celsius in a kettle. For the same amount of heat, how many kilograms of 18.0 celsius air would you be able to warm to 30.5 degrees? Make the simplifying assumption that air is 100% $$N_2$$.

C)What volume would this air occupy at 18.0 celsisu and a pressure of 1.11 atm ?

I'm pretty sure if i figure out B i can solve C

2)
A) How much heat does it take to increase the temperature of n moles of a diatomic ideal gas by an amount $$\Delta\,T$$near room temperature if the gas is held at constant volume? Use R for ideal gas constant.

Well $$C_v =\frac{5}{2} R$$ but this doesnt include any temperature changes so what else is available to use?

B)What is the answer to the question in part (A) if the gas is monatomic rather than diatomic?

Again i think if i can figure out A i can answer B

nvm figured these out but still need help on the question in other thread....help pleasse

Last edited: Jun 19, 2006
2. Jun 20, 2006

### lightgrav

1a) Why not use it ... isn't N_2 diatomic?
The issue is to get Specific Heat Capacity in familiar units ... [J/kg/K].
1b) The ambiguity here is that Cv (part a) is NOT equal to Cp.
1c) Apparently, this air is in a Pressure container, so it CAN be kept at V.

2) "doesn't include any Temperature change" What do you think Cv IS?