1. A cylinder that has a piston contains one mole of H2H2 and undergoes an expan

Question

1. A cylinder that has a piston contains one mole of H2H2 and undergoes an expansion that doubles the initial volume of the gas. How much heat is transferred to or from the gas?

EXPLAIN YOUR ANSWER

a) Heat flows into the gas by an amount greater than the mechanical work WW.

b) Heat flows into the gas by an amount less than the mechanical work WW.

c) Heat flows out of the gas by an amount greater than the mechanical work WW.

d) Heat flows out of the gas by an amount less than the mechanical work WW.

Explanation / Answer

Option A is correct. I.e. heat flows into the system which must be more than the mechanical work we will get out of the system.

To understand this recall concepts of first law of thermodynamics.

dQ= dU + dW

Assuming everything ideal.. no heat lost in the surrounding. Whatever amount of heat we will provide to the gas dQ , a part of it will be used to increase internal energy of the gas dU and remaining part of heat provided will be achieved as work output.. which in turn must be less than dQ .

This is very intrinsic property of all engines.This is why no engine is 100 % efficient. Even most ideal engine " Carnot engine" is not 100 % efficient.

I hope i made it clear. Rate me if u like my effort. Thanks

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