Hess’s Law → sum of ΔH° of individual steps is equal to ΔH° of overall reaction (ΔH°rxn)
Reaction 1: C(s)+2H2(g)→CH4(g) ΔH1 =−74.6kJ
Reaction 2: C(s)+2Cl2 (g)→CCl4(g) ΔH2=−95.7kJ
Reaction 3: H2 (g)+Cl2 (g)→2HCl(g) ΔH3=−184.6kJ
Overall reaction: CH4(g)+4Cl2(g)→CCl4(g)+4HCl(g) ΔH°rxn = ??
To get overall eqn:
CH4(g) → C(s)+2H2(g) ΔH1,rev =+74.6kJ
[H2 (g)+Cl2 (g)→ 2HCl(g)] x 2 2(ΔH3)
Calculate ΔHrxn for the following reaction:
Use the following reactions and given ΔH′s.
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