Question

The values of dissociation constants of some acids (at ${25^ \circ }C$ ) are as follows. Indicate which is the strongest acid in water?
A. $1.4 \times {10^{ - 2}}$
B. $1.6 \times {10^{ - 4}}$
C. $4.4 \times {10^{ - 10}}$
D. $4.3 \times {10^{ - 7}}$

Answer 1

Hint: The strength of the acid increases with the acid dissociation constant. An acid is something that can give a base and a proton \[\left( {{H^ + }} \right)\] . The acid is nearly entirely dissociated if the equilibrium position is much to the right. This type of acid is strong, as we say.

Complete step-by-step answer:A dissociation constant is a particular kind of equilibrium constant used in chemistry, biochemistry, and pharmacology to measure an object's tendency to break down into its component parts, such as when a complex disintegrates into its component molecules or a salt disintegrates into its component ions.
By examining the equilibrium constant for the acid's dissociation, the \[{K_a}\] value can be determined. The more the acid dissociates, the greater the \[{K_a}\] . Strong acids therefore need to dissociate more in water. A weak acid, on the other hand, has a lower tendency to ionise and release a hydrogen ion, leading to a less acidic solution.
The stronger the acid, the more readily it dissociates, and the less tightly its bonds are held together. The \[p{K_a}\] is frequently used to express the \[{K_a}\] value. The degree of dissociation is less severe the higher the value of \[p{K_a}\] . A weak acid has a \[p{K_a}\] value in water that is roughly in the range of 2 to +12. Strong acids are those whose \[p{K_a}\] value is less than or equal to 2.

Option ‘A’ is correct

Note: The \[p{K_a}\] value represents the strength of the acid and is equal to the negative logarithm of \[{K_a}\] , the ionisation constant. Therefore, we can determine the \[{K_a}\] values that will give us the strongest acid by adjusting the \[p{K_a}\] values. Less \[p{K_a}\] \[\left( {p{K_a} = - log{K_a}} \right)\] and more \[{K_a}\] indicate a stronger acid.