# A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 bar from an initial volume of 2.5 L to a final volume of 4.5 L. The change in internal energy, - Chemistry

MCQ

Select the most appropriate option.

A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 bar from an initial volume of 2.5 L to a final volume of 4.5 L. The change in internal energy, ΔU of the gas will be _______.

• –500 J

• + 500 J

• –1013 J

• + 1013 J

#### Solution

- 500 J

Explanation:

Since the container is insulated, this is an adiabatic process.

ΔU = +W = - Pext Δ V = - Pext (V2 - V1)

Initial volume (V1) = 2.5 L = 2.5 dm3

Final volume (V2) = 4.5 L = 4.5 dm3

External pressure (Pext) = 2.5 bar

ΔU = W = - 2.5 bar × (4.5 dm3 - 2.5 dm3)

= - 5.0 dmbar × (100 "J")/(1 "dm"^3 "bar")

= - 500 J

Concept: Chemical Thermodynamics
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#### APPEARS IN

Balbharati Chemistry 12th Standard HSC for Maharashtra State Board
Chapter 4 Chemical Thermodynamics
Exercise | Q 1.02 | Page 86