Question

Which of the following acids, listed with their ionization constant at ${25}^{o}C$, is the strongest?

• A. Nitrous acid $\left(HN{O}_2\right)K_i=4.5\times {10}^{-4}$
• B. Formic acid $\left(HCH{O}_2\right)K_i=1.8\times {10}^{-4}$
• C. Benzoic acid $\left(H{C}_7{H}_5{O}_2\right)K_i=6.3\times {10}^{-5}$
• D. Acetic acid $\left(H{C}_2{H}_3{O}_2\right)K_i=1.8\times {10}^{-5}$
• E. Hydrocyanic acid $\left(HCN\right)K_i=4.0\times {10}^{-10}$

Answer 1

Answer: (A)

Nitrous acid $\left(HN{O}_2\right)K_i=4.5\times {10}^{-4}$

Acid (stronger) $\Rightarrow$ Higher $Ka$ $\Rightarrow$ Higher $K_1$

So, $4.5\times {10}^{-4}\Rightarrow {HNO}_2$