Question

Consider two acids: Cl2CHCO2H (dichloroacetic acid, pKa = 1.3) and HCO2H (formic acid, pKa = 3.8). Which acid has the larger Ka? Select the single best answer.

Answer 1

Answer:

$Cl_2CHCO_2H$

Explanation:

pKa is defined as the negative logarithm of Ka.

Thus,

pKa = -log Ka

Thus, larger the value of Ka, smaller is the value of pKa.

Given that:-

$Cl_2CHCO_2H$ has a pKa = 1.3

$HCO_2H$ has a pKa = 3.8

Thus, lower value of pKa has the larger Ka which is $Cl_2CHCO_2H$, dichloroacetic acid ( 1.3 < 3.8 ) .