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Multiple Choice
What is the approximate Keq for the following acid/base reaction?
A
~ 109
B
~ 105
C
~ 10−5
D
~ 10−9
Verified step by step guidance
1
Identify the acid and base on both sides of the reaction. In this reaction, ethanol (C2H5OH) is the base and HBr is the acid on the reactant side. On the product side, the conjugate acid is protonated ethanol (C2H5OH2+) and the conjugate base is bromide ion (Br−).
Determine the pKa values of the acid and conjugate acid. The pKa of HBr is approximately -9, and the pKa of ethanol (as an acid) is approximately 16.
Calculate the difference in pKa values between the acid and the conjugate acid. This is done by subtracting the pKa of the conjugate acid (ethanol) from the pKa of the acid (HBr): pKa(HBr) - pKa(C2H5OH) = -9 - 16.
Use the relationship between pKa and Keq to estimate the equilibrium constant (Keq). The equation is: Keq = 10^(pKa(conjugate acid) - pKa(acid)).
Substitute the calculated pKa difference into the equation to find the approximate Keq. This will give you an idea of the equilibrium position of the reaction.