Question

What amount of heat must be supplied to 2.0 × 10¯² kg of nitrogen (at room temperature) to raise its temperature by 45 °C at constant pressure ? (Molecular mass of N² = 28; R = 8.3 J mol–¯¹ K¯¹.)

Answer 1

Given, the mass of nitrogen is 20× 10 −2  kg or 20 g, rise in temperature of nitrogen is 45 °C, molecular mass of nitrogen is 28 and universal gas constant is 8.3 J/ mol⋅K .

Let n be the number of moles, then

n= m M

Here, m is the mass of nitrogen and M is the molar mass of nitrogen.

Substitute the value in the above expression.

n= 20 28 =0.714

Let C p be the molar specific heat at constant pressure for a diatomic gas, then

C p = 7 2 R

Here, R is the universal gas constant.

Substitute the value in the above expression.

C p = 7 2 ×8.3 =29.05 J/ mol⋅K

Let Q be the amount of heat supplied to nitrogen, then

Q=n C p ΔT

Here, ΔT is the temperature rise.

Substitute the values in the above expression,

Q=0.714×29.05×45 =934 J

Hence, the amount of heat supplied to nitrogen is 934 J.