Hello everyone!
This is the problem:
Find the heat of AgCl formation at 150°С, if Δ
f H (AgCl(s)) = -126,8 kJ/mol, taking into acount the following molar heat capacities:
Cp (Ag)= 23,97 + 5,28*10
–3Т – 0,25*10
5Т
–2 J/(mol*К);
Cp (Cl2) = 36,69 + 1,05*10
–3Т – 2,52*10
5Т
–2 J/(mol*К);
Cp (AgCl (s)) = 62,26 + 4,18*10
–3Т – 11,30*10
5Т
–2 J/(mol*К).
The answer in the textbook: –125,35 kJ/mol.
This how I tried to solve it:
Ag + (1/2)Cl2 = AgCl
Δ a = 62.26-23.97-0.5*36.69=36.445=36.44
Δb=4.18*10
-3 - 5.28*10
-3 - 0.5*1.05*10
-3= -1.625*10
-3 = -1.63*10
-3Δ c' = -11,30*10
5+0,25*10
5+0,5*2,52*10
5 = -979000
Δ Cp = 36.44-1.63*10
-3T-979000T
-2ΔH = -126800 + 36.44(423-298)-0.5*1.63*10
-3*(423
2-298
2)-979000(1/298-1/423) = -123.3 kJ/mol.
Could you please help me to find the mistake?
maybe something's wrong with my rounding up?