ThermochemistryHard

Question

 

Reaction involving gold have been of particular intersect to alchemists. Consider the following reactions,
    Au(OH)3 + 4 HCl  → HAuCl4 + 3H2O,        ᐃH = - 28 kcal
    Au(OH)3 + 4 HBr →  HAuBr4 + 3H2O,       ᐃH = - 36.8 kcal
In an experiment there was an absorption of 0.44 kcal when one mole of HAuBr4 was mixed with 4 moles of HCl. What is the percentage conversion of HAuBr4 into HAuCl4 ?

 

Options

A.0.5%
B.0.6%
C.5%
D.50%

Solution

HAuBr4 + 4HCl HAuCl4 + 4HBr
            ᐃH = - 28 + 36.8
                 = 8.8 kcal
% converssion is × 100 = 5.

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