One kg of air is heated in a closed rigid vessel

[manal950]

Homework Statement

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

Homework Equations

Q = mXCX(T2 - T1 )

The Attempt at a Solution

please can anyone explain to me how I can solve this question

and is R and Cv must be in same unit

my answer :

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

 

[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
add Q to get work

 

[manal950]

I don't understand clearly can please help ?

 

[Chestermiller]

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.

 

[manal950]

thanks so much