Chloroform, CHCl 2 , is formed by thefollowing reaction: Desired ·H rxn equation

Question

Chloroform, CHCl2, is formed by thefollowing reaction:

Desired ·Hrxn equation: CH4 (g) +3Cl2 (g) + 3HCl (g) + CHCl3 (g)

Determine the enthalpy change for this reaction using thefollowing:

2C (graphite) + H2 (g) + 3Cl2 (g) ·2CHCl3 (g) ·H?f = -103.1 kJ/mol
CH4 (g) + 2O2 (g) · 2 H2O(l) + CO2 (g)     ·H ?f = -890.4kJ/mol
2HCl (g) · H2 (g) + Cl2 (g)       ·H?f = +184.6 kJ/mol
C (graphite) + O2 (g) · CO2(g)                           ·H ?f = -393.5 kJ/mol
H2 (g) +1/2 O2 (g) · H2O(l)                                ·H ?f = -285.8 kJ/mol

answer should be -103.1 kJ but I couldn't figure it out.
This is an extra problem my instructor assigned and is not in thetextbook. Please use Hess's Law to figure out. Thanks alot!

Explanation / Answer

If you do this: 1/2 (2C (graphite) + H2 (g) + 3Cl2 (g)· 2CHCl3 (g)) (·H ?f = -103.1 kJ/mol)1/2 CH4 (g) + 2O2 (g) · 2 H2O(l) + CO2 (g)     ·H ?f = -890.4 kJ/mol -3/2 (2HCl (g) · H2 (g) + Cl2 (g))       (·H?f = +184.6 kJ/mol) -3/2 -1 (C (graphite) + O2 (g) · CO2 (g))                          (·H ?f = -393.5 kJ/mol) -1 -2 (H2 (g) +1/2 O2 (g) ·H2O (l))                                 (·H ?f = -285.8 kJ/mol) -2 You get..... C (graphite) + 1/2H2 (g) + 3/2Cl2 (g)· CHCl3 (g) ·H ?f = -51.55 kJ/mol CH4 (g) + 2O2 (g) · 2 H2O(l) + CO2 (g)           ·H?f = -890.4 kJ/mol 3/2H2 (g) + 3/2Cl2 (g) · 3HCl(g)      ·H ?f =-276.9 kJ/mol CO2 (g) · C (graphite) + O2(g)                               ·H ?f = +393.5 kJ/mol 2H2O (l) · 2H2 (g) + O2 (g)                                   ·H ?f = +571.6 kJ/mol -------------------------------------------------------------------------------- CH4 (g) + 3Cl2 (g) · 3HCl (g) +CHCl3(g)              ·H ?f = -253.75 kJ/mol Thus the answer provided was incorrect and should be -253.75kJ/mol

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