Anonymous asked in Science & MathematicsChemistry · 1 month ago

Wondering if someone could help me with this chemistry problem that I have ?

1. The enthalpy of combustion (ΔH°c) of 2,3-dimethylbutane (C6H14) is -4154.90 kJ/mol. Using the appropriate information given below, calculate the enthalpy of formation (ΔH°f), in kJ/mol, for 2,3-dimethylbutane.

Report your answer to two decimal places.

ΔH°f (CO2 (g)) = -393.51 kJ/mol

ΔH°f (H2O (l)) = -285.83 kJ/mol

2. Determine the mass (in g) of 2,3-dimethylbutane produced, if ΔH° was determined to be -211.11 kJ during an experiment in which 2,3-dimethylbutane was formed.

Report your answer to three significant figures.

1 Answer

  • DavidB
    Lv 7
    1 month ago

    the thermochemical equation is

    2C6H14 + 19O2 ---> 12CO2 + 14H2O ΔH°c = -4154.90 kJΔH°c

    now from heats of combustion you also know

    ΔH°c = sum ΔH°f(products) - sum ΔH°f(reactants)

    you know ΔH°f for the products and know ΔH°c so the only unknown is ΔH°f for the reactants and thus determine ΔH°f for C6H16 (ΔH°f for O2 is 0 kJ/mol).

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