Solution Found!
(a) How much heat is released when 25.0 g of methane bums
Chapter 5, Problem 84P(choose chapter or problem)
Problem 84P
(a) How much heat is released when 25.0 g of methane bums in excess O2 to form gaseous CO2 and H2O?
(b) Calculate the temperature of the product mixture if the methane and air are both at an initial temperature of 0.0°C. Assume a stoichiometric ratio of methane to oxygen from the air, with air being 21% O2 by volume (c of CO2 = 57.2 J/mol·K; c of H2O(g) = 36.0 J/mol·K; c of N2 = 30.5 J/mol·K).
Questions & Answers
QUESTION:
Problem 84P
(a) How much heat is released when 25.0 g of methane bums in excess O2 to form gaseous CO2 and H2O?
(b) Calculate the temperature of the product mixture if the methane and air are both at an initial temperature of 0.0°C. Assume a stoichiometric ratio of methane to oxygen from the air, with air being 21% O2 by volume (c of CO2 = 57.2 J/mol·K; c of H2O(g) = 36.0 J/mol·K; c of N2 = 30.5 J/mol·K).
ANSWER:
Solution 84P
Step 1
(a) Here we have to calculate how much heat is released when 25.0 g of methane bums in excess O2 to form gaseous CO2 and H2O.
1st we have to write a balanced equation for the combustion of methane.
CH4 (g) + 2O2 (g) → CO2(g) + 2H2O (g)
Mass of methane burn = 25.0 g
Mol of methane = 25.0 g CH4 = 1.558 mol CH4
Now we have to calculate the heat change during the combustion reaction,
=
-
= [1 mol (CO2(g))] + [1 mol (
CH4(g) + 2 mol (
O2(g))]
= [1 mol (-393.5 kJ/mol) + 2 mol (-241.826 kJ/mol)] - [1 mol (-74.87 kJ/mol) + 2 mol (0.0 kJ/mol)]
= -802.282 kJ/mol CH4
The amount of heat released can be calculated as,
1.5586 mol CH4 = -1250.4 = -1.25
103 kJ
Thus the amount of heat released can be calculated as -1.25 103 kJ.