Answer to Question #193708 in General Chemistry for Earl

Question

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

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

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

2. Calculate the ∆H for the reaaction:

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

  given:

     ∆HrCO2 (g)= -393.5 kJ/mol;

     ∆HrSO2= -296.8 kJ,/mol;

     ∆HrCS2 (I) = 87.9 kJ/mol

Answer 1

1. Heat of hydrogenation $+$ heat of combustion of ethylene$-$heat of combustion of ethane

$=52.3kJ/mol-(-84.5kJ/mol)=136.8kJ/mol$

2.$\Delta H_{reaction}=\Delta H_rCs-(\Delta H_rSO_2+\Delta H_rCO_2)$

$=87.9kJ/mol-[(-393.5kJ/mol)+(-296.8kJ/mol)]=-751.2kJ/mol$