0.0884 moles of a diatomic gas are in a piston. When the piston
is compressed, the temperature
drops by 18.8 K, and 83.7 J of
heat flow out. Find W.
(Be careful with + and - signs.
+W = expansion, +Q = added,
+AU = temp goes up)
(Unit = J)

W = - 118.24 J (negative sign shows that work is done on piston)

Explanation:

First, we find the change in internal energy of the diatomic gas by using the following formula:

where,

ΔU = Change in internal energy of gas = ?

n = no. of moles of gas = 0.0884 mole

Cv = Molar Specific Heat at constant volume = 5R/2 (for diatomic gases)

Cv = 5(8.314 J/mol.K)/2 = 20.785 J/mol.K

ΔT = Rise in Temperature = 18.8 K

Therefore,

Now, we can apply First Law of Thermodynamics as follows:

where,

ΔQ = Heat flow = - 83.7 J (negative sign due to outflow)

W = Work done = ?

Therefore,

W = - 118.24 J (negative sign shows that work is done on piston)

c. magnitude and direction

cant without the picture! ?