Question

2.2 g of nitrous oxide (N₂O) gas is cooled at a constant pressure of 1 atm from 310 K to 270 K causing the compression of the gas from 217.1 mL to 167.75 mL. The change in internal energy of the process, Δ U is '- x' J. The value of 'x' is ______.

(Nearest integer)

(Given: atomic mass of N = 14 g mol^-1 and of O = 16 g mol^-1, Molar heat capacity of N₂O is 100 JK^-1 mol^-1)

Options

• 195

• 200

• 150

• 65

Answer 1

2.2 g of nitrous oxide (N₂O) gas is cooled at a constant pressure of 1 atm from 310 K to 270 K causing the compression of the gas from 217.1 mL to 167.75 mL. The change in internal energy of the process, Δ U is '- x' J. The value of 'x' is 195. 

Explanation:

T₁ = 310 K, T₂ = 270 K

ΔT = T₂ – T₁ = 270 K - 310 K = - 40 K

q_p = n C_p ΔT

`= 2.2/44 xx 100 × (- 40)`

= - 200 J

ΔV = V₂ – V₁

= (167.75 – 217.1) mL

= 49.35 mL

w = - P_ext × DV

w = - (1) × `((- 49.35)/1000)` atm L

w = + 0.04935 atm L

w = 0.04935 × 101.3 J

w = 4.99 J ~ 5 J

ΔU = q + w

= - 200 + 5

= - 195 J

So, the value of x is 195.