Question

A gas expands against a constant external pressure of 2.00 atm, increasing its volume by 3.40 L. Simultaneously, the system absorbs 400 J of heat from its surroundings. What is $\Delta E$, in joules for this gas ?

• A. -689
• B. -289
• C. 400
• D. 289

Answer 1

Answer: (B)

-289

First law of thermodynamics:

This law is based upon the conservation of energy,

The mathematical form of the first law of thermodynamics is:

$\Delta E=q+w$

Here

$\Delta E$ = Change in internal energy

$q=$ Absorbed heat by the system

$w=$ Work done on the system.

So,

$\Delta E=q-P\Delta V$

$\Delta E=400-2\times 3.4\times 101.33J$

$\Delta E=-289J$