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# Answer to Question #203847 in General Chemistry for Monique Keith Anto

Question #203847

Topic: Enthalpy and Hess Law

1. Calculate the heat of hydrogenation of ethane, C2H4 given the following thermochemical equations:

2 C (graphite) + 3 H2 (g) ---> C2H6 (g). ∆Hf= -84.5 kJ/mol

2 C (graphite) + 2 H2 (g) ---> C2H4 (g). ∆Hf= 52.3 kJ/mol

2. Calculate the ∆H for the reaction:

CS2 (I) + 2 O2 (g) CO2 (g) + 2 SO2 (g)

Given:

∆Hf CO2 (g) = - 393.5 kJ/mol

∆Hf SO2 = - 296.8 kJ/mol

∆Hf CS2 (I) = 87.9 kJ/mol

1
2021-06-07T03:24:10-0400

1) we have to calculate heat of hydrogenation of ethane "C_2H_6"

2 C (graphite) + 3 H2 (g) ---> C2H6 (g). ∆Hf= -84.5 kJ/mol..........................1

2 C (graphite) + 2 H2 (g) ---> C2H4 (g). ∆Hf= 52.3 kJ/mol.............................2

for that we will subtract equation 2 from equation 1.

and we will get,

"C_ \n2\n\u200b\n H _\n4\n\u200b\n (g)+H_ \n2\n\u200b\n (g)\u27f6C _\n2\n\u200b\n H _\n6\n\u200b\n (g)"

and "\\Delta H_f =\\Delta H_{f1}-(-\\Delta H_{f2})"

"\\Delta H_{f}=-84.5+52.3\\\\"

"\\Delta H_{f}(ethane)= 32.2" kJ/mol

2) ∆H for the reaction:

CS2 (I) + 2 O2 (g ) -----> CO2 (g) + 2 SO2 (g)

we know that,

"\\Delta{H}_{reaction}=\\sum{\\Delta{H_{products}-\\sum\\Delta{H}_{reactants}}}"

"=\u2212393.5+2(\u2212296.8)\u221287.9"

"=\u22121075kJ\/mol"

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