# One kg of air is heated in a closed rigid vessel

1. Nov 3, 2012

### manal950

1. The problem statement, all variables and given/known data

One kg of air is heated in a closed rigid vessel such its temperature changes from 27 C to 427 C . Find the heat transfered
and change in internal energy .
Assume : -
R= 0.287 KJ/kg k
Cv = 0786 KJ/Kg k

2. Relevant equations

Q = mXCX(T2 - T1 )

3. The attempt at a solution

please can any one explain to me how I can solve this question

and is R and Cv must be in same unit

heat transfer = 1 X 0.786 X 10 (700-300 )

314.4X 10^3 KJ ( is the unit correct )

and about second one I don't have any idea for solve it

2. Nov 3, 2012

### fzngagan

ΔU=q + w(external)
w=work
as you posted Cv then volume is constnt so change in pressure should be taken.so by Gay Lussacs law P=kT
thereforeP1/P2=T1/T2
so you can find Work by volume*change in pressure

3. Nov 3, 2012

4. Nov 3, 2012

### Staff: Mentor

Since the container is rigid, there is no volume change and no work is done. The heat transferred is equal to the change in internal energy.

5. Nov 3, 2012

### manal950

thanks so much