Question

which of the following substances is responsible for donating h+ ions to act as a buff
carbonic acid
carbon monoxide
oxygen
carbon dioxide

Explanation:

Carbonic acid ($H_2CO_3$) can dissociate to donate $H^+$ ions. The dissociation reaction is $H_2CO_3
ightleftharpoons H^++HCO_3^-$. When there is an increase in $OH^-$ ions (which would consume $H^+$), carbonic acid can release more $H^+$ to counteract the change in pH. Carbon monoxide ($CO$), oxygen ($O_2$), and carbon dioxide ($CO_2$) do not have the ability to donate $H^+$ ions in the context of buffering in the way described.

Answer:

Carbonic acid