Question

Find the change in internal energy of 40 g of Argon gas when its change in temperature is 100 K.
(Given degree of freedom of argon is 3)

• A. 4800 J
• B. 3800 J
• C. 5100 J
• D. 1250 J

Answer 1

The correct option is D 1250 J

Since, we know $\Delta U=\frac{f}{2}nRdT$
where $\Delta U$= internal energy of the gas
n = number of moles of gas = $\frac{40}{40}$ = 1 mole
We know, f = degree of freedom = 3
$\Delta U=\frac{3}{2}\times 1\times 8.314\times \Delta T$
So, $\Delta U=\frac{3}{2}\times 1\times 8.314\times 100$
or,
$\Delta U=1247J$ ~ 1250 J