# A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 ml to 375 ml at a constant temperature of 37°C. As it does so, it absorbs 208J of heat. The value of q and w for the process will be: (In 7.5 = 2.01) Option 1) q = -208 J, w = +208 J Option 2) q = 208 J, w = 208 J Option 3) q = 208 J, w = -208 J Option 4) q = -208 J, w = -208 J

As we discussed in concept

First law of Thermodynamics -

Energy of universe is always conserved or total energy of an isolated system is always conserved

$\Delta E= q + W$

- wherein

$\Delta E=$ Internal Energy

$q=$ Heat

$W=$ work

Process is isothermal reversible expansion.

Therefore, $\Delta E=0$

Now using first law of thermodynamics.

$\Delta E=\:g+W;g=208\:J\:(given)$

W = -g

= - 208 J

Option 1)

q = -208 J, w = +208 J

This option is incorrect.

Option 2)

q = 208 J, w = 208 J

This option is incorrect.

Option 3)

q = 208 J, w = -208 J

This option is correct.

Option 4)

q = -208 J, w = -208 J

This option is incorrect.

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