Question

A gas expands isothermally to double its volume. The rms speed of its molecules will be
(A) Increased
(B) Decreased
(C) Remains constant
(D)
First increases and then decreases​

Answer 1

Answer:

The answer is a option A

Answer 2

Answer:

A gas expands isothermally against a constant external pressure of 1 atm from a volume of 10 dm

3

to a volume of 20 dm

3

. It absorbs 300 J of thermal energy from its surrounding. The △U is:

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ANSWER

In general,

W=−∫

V

1

V

2

PdV=−P(V

2

−V

1

)

W=−(1 atm)(20−10)=−10 dm

3

atm.

=−1atm×10 dm

3

×

0.08206 dm

3

−atm/K/mol

8.314 J/K/mol

=−1013 J

According to 1st law of thermodynamics,

△U=q+W=800 J+(−1013 J)=−213 J