Question

For the reaction H2PO4- HAsO4 2-HPO4 2-+H2AsO4-
what species are a conjugate acid-base pair?

Answer 1

Ionic equation:

The acid and base in a conjugate pair differ by only one proton . The acid loses one proton to produce a conjugate base, whereas the base gains a proton to produce its conjugate acid.

loses one proton to produce in this reaction.

Meanwhile, gains one proton to form .

Therefore

• is the conjugate acid , its conjugate base.

• is the conjugate base of , its conjugate acid.

Answer 2

Ionic equation:

`\text{H}_2\text{PO}_4^(-) + \text{HAsO}_4^(2-) \to \text{HPO}_4^(2-) + \text{H}_2\text{AsO}_4^(-)`

The acid and base in a conjugate pair differ by only one proton
`\text{H}^(+)`. The acid loses one proton to produce a conjugate base, whereas the base gains a proton to produce its conjugate acid.

`\text{H}_2\text{PO}_4^(-)` loses one proton to produce
`\text{HPO}_4^(2-)` in this reaction.

`\text{H}_2\text{PO}_4^(-) \to \text{H}^(+) + \text{HPO}_4^(2-)`

Meanwhile,
`\text{HAsO}_4^(2-)` gains one proton to form
`\text{H}_2\text{AsO}_4^(-)`.

`\text{HAsO}_4^(2-) + \text{H}^(+) \to \text{H}_2\text{AsO}_4^(-)`

Therefore

• 
  `\text{H}_2\text{PO}_4^(-)` is the conjugate acid
  `\text{HPO}_4^(2-)`, its conjugate base.
• 
  `\text{HAsO}_4^(2-)` is the conjugate base of
  `\text{H}_2\text{AsO}_4^(-)`, its conjugate acid.