Calculate ΔH°rxn for the following: (Hess’s Law of Heat Summation)?

Calculate ΔH°rxn for the following:

SiO2(s) + 4 HF(g) –> SiF4(g) + 2 H2O(l)

in kJ.

Please briefly explain for me. i think i have the basics down. so hopefully i will understand the explanation

Thanks!

1 Answer

  • SiO2(s) + 4 HF(g) –> SiF4(g) + 2 H2O(l)

    what you need are the values for ΔH formation of each compound.

    H formation SiO2 = -911 kJ/mole…..1 mole

    H formation HF = -268.6 kJ/mole…..4 moles

    H formation SiF4 = -1609.428 kJ/mole…..1 mole

    H formation H2O = -285.83 kJ/mole…..2 moles

    ΔH°rxn = products – reactants

    ΔH°rxn = (-1609.428 + 2(-285.83)) – (-911 + 4(-268.6))

    ΔH°rxn = -2181.09 – (-1985.4) = -195.69kJ

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