Question

(a) The hydrogen oxalate ion \(\left(\mathrm{HC}_{2} \mathrm{O}_{4}{ }^{-}\right)\) is amphiprotic. Write a balanced chemical equation showing how it acts as an acid toward water and another equation showing how it acts as a base toward water. (b) What is the conjugate acid of \(\mathrm{HC}_{2} \mathrm{O}_{4}^{-} ?\) What is its conjugate base?

Short answer

(a) Acidic behavior: \( \mathrm{HC}_{2} \mathrm{O}_{4}^{-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{C}_{2} \mathrm{O}_{4}^{2-} + \mathrm{H}_{3}\mathrm{O}^{+} \) Basic behavior: \( \mathrm{HC}_{2} \mathrm{O}_{4}^{-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{H}_{2}\mathrm{C}_{2}\mathrm{O}_{4} + \mathrm{OH}^{-} \) (b) Conjugate acid: H2C2O4. Conjugate base: C2O42-.

Step-by-step solution

Write the equation for acidic behavior of HC2O4-

To show how hydrogen oxalate ion acts as an acid when reacting with water, it must donate a proton (H+) to water. The balanced chemical equation for this acidic behavior is: \( \mathrm{HC}_{2} \mathrm{O}_{4}^{-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{C}_{2} \mathrm{O}_{4}^{2-} + \mathrm{H}_{3}\mathrm{O}^{+} \)

Write the equation for basic behavior of HC2O4-

To show how hydrogen oxalate ion acts as a base when reacting with water, it must accept a proton (H+) from water. The balanced chemical equation for this basic behavior is: \( \mathrm{HC}_{2} \mathrm{O}_{4}^{-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{H}_{2}\mathrm{C}_{2}\mathrm{O}_{4} + \mathrm{OH}^{-} \)

Identify the conjugate acid of HC2O4-

When the hydrogen oxalate ion acts as a base and accepts a proton (H+), the resulting species is its conjugate acid. Based on the equation in Step 2: Conjugate acid of HC2O4- is H2C2O4.

Identify the conjugate base of HC2O4-

When the hydrogen oxalate ion acts as an acid and donates a proton (H+), the resulting species is its conjugate base. Based on the equation in Step 1: Conjugate base of HC2O4- is C2O42-.