In: Chemistry
Consider the following data: ΔvapH = 5.56 kJ/mol Specific heat capacity of N2(g) = 29.2 J mol-1 K-1 Specific heat capacity of N2(l) = 56.04 J mol-1 K-1 Boiling point of N2 = 77.355 K What is the energy in the form of heat released when 450 grams of nitrogen gas at 23.0 °C is converted to liquid nitrogen at -200.0 °C? Select one: a. 364 kJ b. 196 kJ c. 392 kJ d. 17.1 kJ
Ti = 23.0 oC
Tf = -200.0 oC
Cg = 29.2 J/mol.oC
boiling point = 77.355 K = 77.355 - 273.15 oC = -195.795 oC
Lets convert mass to mol
Molar mass of N2 = 28.02 g/mol
number of mol
n= mass/molar mass
= 450.0/28.02
= 16.06 mol
Heat released to convert vapour from 23.0 oC to -195.795 oC
Q1 = n*Cg*(Ti-Tf)
= 16.06 mol * 29.2g J/mol.oC *(23--195.795) oC
= 102604.0792 J
Lv = 5.56KJ/mol = 5560J/mol
Lets convert mass to mol
Molar mass of N2 = 28.02 g/mol
number of mol
n= mass/molar mass
= 450.0/28.02
= 16.06 mol
Heat released to convert gas to liquid at -195.795 oC
Q2 = n*Lv
= 16.06 mol *5560 J/mol
= 89293.3619 J
Cl = 56.04 J/mol.oC
Lets convert mass to mol
Molar mass of N2 = 28.02 g/mol
number of mol
n= mass/molar mass
= 450.0/28.02
= 16.06 mol
Heat released to convert liquid from -195.795 oC to -200.0 oC
Q3 = n*Cl*(Ti-Tf)
= 16.06 mol * 56.04l J/mol.oC *(-195.795--200) oC
= 3784.5 J
Total heat released = Q1 + Q2 + Q3
= 102604.0792 J + 89293.3619 J + 3784.5 J
= 195682 J
= 196 KJ
Answer: 196 KJ