Part A
Calculate the standard enthalpy change for the reaction

2A+B --->2C +2D
Use the following data:

Substance Delta H(kJ/mol)
A -263
B -391
C +203
D -523
Express your answer in kilojoules.

Express your answer numerically in kilojoules
For the reaction given in Part A, how much heat is absorbed when 3.80 mol of A reacts?

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  1. I have an answer of 271 kJ/rxn for part A. Check your math.
    For part B,
    271 kJ/2 mol x (3.80 mol) = ??

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  2. At last, someone comes up with the "right" anwesr!

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  3. Substance

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  4. Calculate the standard enthalpy change for the reaction
    Use the following data:
    Substance ΔH∘f
    A -275
    B -389
    C 195
    D -503
    Express your answer to three significant figures and include the appropriate units.

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  5. So for part on you will use the Delta H of products subtracted by the Delta H of reactants. using the values given and multiplying by the coefficient of the compound.

    A. [2(203)+(-523)]-[2(-263)+(-391)] = Delta Hrxn which would be 932kJ

    for part B the difference of the two moles from the first problem then the new moles giving then will be multiplied by the answer from part A

    B. 3.8mols/2moles = 1.9 moles 1.9moles x 932kJ = H H = 1770.8kJ

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