Chapter 2, Problem 65P

a. Given the K_a values, estimate the pK_a value of each of the following acids without using a calculator (that is, is it between 3 and 4, between 9 and 10, and soon?):

1. 1. nitrous acid (HNO₂), K_a = 4.0 × 10^–4
2. 2. nitric acid (HNO₃), K_a = 22
3. 3. bicarbonate ( ${\text{HCO}}_3^{-}$), K_a. = 6.3 × 10^–11
4. 4. hydrogen cyanide (HCN), K_a. = 7.9 × 10^–10
5. 5. formic acid (HCOOH), K_a = 2.0 × 10^–4
6. 6. phosphoric acid (H₃PO₄), K_a = 2.1

b. Determine the exact pK_a values, using a calculator.

c. Which is the strongest acid?