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Chemistry LibreTexts

Solutions

  • Page ID
    11098
  • 1. Calculate the DHorxn from the DHof for the following reaction:

    a) PbO (s) + CO (g) -------> Pb (s) + CO2 (g) DHorxn = -65.7 kJ

    b) SiH4 (g) + 2 O2 (g) -------> SiO2 (s) + 2 H2O (l) DHorxn = -1516.8 kJ

    c) 2 FeS2 (s) + 5.5 O2 (g) -------> Fe2O3 (s) + 4 SO2 (g) DHorxn = -1656.4 kJ

    2. Determine the DHrxn using Hess' Law

    a) Determine the enthalpy of formation for MnO2 (s)

    Mn (s) + O2 (g) --------> MnO2 (s)

    Given:

    4 Al (s) + 3 O2 (g) -------> 2 Al2O3 (s) DHrxn = -3352 kJ/mol

    4 Al (s) + 3 MnO2 (s) -------> 3 Mn (s) + 2 Al2O3 (s) DHrxn = -1937 kJ/mol

    DHf = -471.7 kJ/mol

    b) Determine the heat of hydrogenation for

    C3H4 (g) + 2 H2 (g) --------> C3H8 (g)

    Given:

    2 H2 (g) + O2 (g) -------> 2 H2O (l) DHrxn = -571.6 kJ/mol

    C3H4 (g) + 4 O2 (g) -------> 3 CO2 (g) + 2 H2O (l) DHrxn = -1937 kJ/mol

    C3H8 (g) + 5 O2 (g) -------> 3 CO2 (g) + 4 H2O (l) DHrxn = -2220 kJ/mol

    DHrxn = -288.6 kJ/mol