2. which of the following are amphoteric in aqueous solution? for those that are amphoteric, write one…

2. which of the following are amphoteric in aqueous solution? for those that are amphoteric, write one equilibrium equation showing it acting as an acid and one equilibrium equation showing it acting as a base.\nnh₄⁺, h₂po₄⁻, hcl, hc₂o₄⁻, ch₃nh₃⁺, hco₃⁻

2. which of the following are amphoteric in aqueous solution? for those that are amphoteric, write one equilibrium equation showing it acting as an acid and one equilibrium equation showing it acting as a base.\nnh₄⁺, h₂po₄⁻, hcl, hc₂o₄⁻, ch₃nh₃⁺, hco₃⁻

Answer

Explanation:

Step1: Recall the definition of amphoteric

An amphoteric substance can act as both an acid (donate a proton) and a base (accept a proton).

Step2: Analyze each species

  • $NH_4^+$: Can only donate a proton to act as an acid ($NH_4^+\rightleftharpoons NH_3 + H^+$), but it cannot easily accept a proton to act as a base. So it is not amphoteric.
  • $H_2PO_4^-$: As an acid: $H_2PO_4^-\rightleftharpoons HPO_4^{2 -}+H^+$; as a base: $H_2PO_4^- + H^+\rightleftharpoons H_3PO_4$. It is amphoteric.
  • $HCl$: Can only donate a proton ($HCl\rightleftharpoons H^++Cl^-$), it cannot act as a base. So it is not amphoteric.
  • $HC_2O_4^-$: As an acid: $HC_2O_4^-\rightleftharpoons C_2O_4^{2 -}+H^+$; as a base: $HC_2O_4^-+H^+\rightleftharpoons H_2C_2O_4$. It is amphoteric.
  • $CH_3NH_3^+$: Can only donate a proton ($CH_3NH_3^+\rightleftharpoons CH_3NH_2 + H^+$), but it cannot easily accept a proton to act as a base. So it is not amphoteric.
  • $HCO_3^-$: As an acid: $HCO_3^-\rightleftharpoons CO_3^{2 -}+H^+$; as a base: $HCO_3^-+H^+\rightleftharpoons H_2CO_3$. It is amphoteric.

Answer:

The amphoteric species are $H_2PO_4^-$, $HC_2O_4^-$ and $HCO_3^-$. For $H_2PO_4^-$: As an acid: $H_2PO_4^-\rightleftharpoons HPO_4^{2 -}+H^+$; as a base: $H_2PO_4^- + H^+\rightleftharpoons H_3PO_4$. For $HC_2O_4^-$: As an acid: $HC_2O_4^-\rightleftharpoons C_2O_4^{2 -}+H^+$; as a base: $HC_2O_4^-+H^+\rightleftharpoons H_2C_2O_4$. For $HCO_3^-$: As an acid: $HCO_3^-\rightleftharpoons CO_3^{2 -}+H^+$; as a base: $HCO_3^-+H^+\rightleftharpoons H_2CO_3$.