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smita smita
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12 years ago
An unknown monoprotic acid has a molar mass of 84.0 g/mol. When 9.70 g of the acid is dissolved in 1.000 L of water, the pH of the solution is 2.780. What is the pKa of the unknown acid?
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#1
12 years ago
moles HA = 9.70 / 84.0 =0.115
initial concentration HA = 0.115 / 1.00 L = 0.115
concentration H+ = 10^-2.780=0.00166 M = concentration A-
concentration HA at equilibrium = 0.115 - 0.00166 =0.113
Ka = ( 0.00166)^2 / 0.113 =0.0000244
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