Question

1. Enthalpy Problem: Show your work neatly and methodically.

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO3:

2 KClO3(s)---> 2 KCl(s) + 3 O2(g) ΔH = -89.4 kJ

a) How much heat is released when 20.224 grams of O2(g) is made?

b) How many grams of O2(g) is made when 96.0 kJ of heat is released?

2. Enthalpy Problem: Show your work neatly and methodically.

2 CH3OH(g) ---> 2 CH4(g) + O2(g) ΔH = +252.8 kJ

a) How much heat is released when 38.5 grams of methane gas, CH4(g), reacts completely with O2(g) to form CH3OH(g) at constant pressure?

b) For a given sample of CH3OH(g), the enthalpy change during the reaction is 82.1 kJ. How many grams of methane gas, CH4(g), are produced?

PLEASE BE SURE TO STATE CLEAR ANSWERS WITH WORK TO DESCRIBE THE METHOD. THANK YOU!!

Answer 1

1. 2 KClO3(s)---> 2 KCl(s) + 3 O2(g) ΔH = -89.4 kJ

a) No of mol of O2 = 20.224/32 = 0.632 mol

heat released = 0.632*-89.4/3 = -18.834 kj

b) 3 mol O2 = 89.4 kj

   x           = 96 kj

x = 96*3/89.4 = 3.22 mol

2.

2 CH3OH(g) ---> 2 CH4(g) + O2(g) ΔH = +252.8 kJ

a)No of mol of CH4 = 38.5/16 = 2.4 mol

2 mol CH4 = 252.8 Kj

2.4 mol CH4 = 252.8*2.4/2 = 303.36 Kj

b)

252.8 kj = 2 mol CH4

82.1 Kj   = X

X = 82.1*2/252.8 = 0.65 mol

No of mol of CH4 produced = 0.65 mol