Question

A gas is allowed to expand at constant temperature from a volume of 1.0 L to 10.1 L against an external pressure of 0.50 atm. If the gas absorbs 250 J of heat from the surroundings, what are the values of q, w and $\Delta E$ ? (Given 1 L atm = 101.0 J)

	q	w	$\Delta E$
A	250 J	-460 J	-210 J
B	-250 J	-460 J	- 710 J
C	250 J	460 J	710 J
D	- 250 J	460 J	210 J

• A. A
• B. B
• C. C
• D. D

Answer 1

Answer: (A)

Since heat is absorbed, $q=+250\text{ J}$

Work done $=-p\left(V_{2} - V_{1}\right)$

$=-50\text{ atm}\times \left(\text{10.1 L} - 1.0 \text{ L}\right)$

$=-0.50\text{ atm}\times 9.1\text{ L}$

$=-0.50\times 9.1\text{ L atm}\times \frac{101.0 \text{ J}}{1 \text{ L atm}}=-460.0\text{ J}$

Also $\Delta E=q+w=250\text{ J}-460\text{ J}=-210\text{ J}$