Question

1. you have a buffer system made up of equimolar amounts of carbonic acid, h₂co₃, and sodium bicarbonate, nahco₃. write equations to show how this buffer behaves when (a) hcl is added and (b) naoh is added.

Explanation:

Step 1: Analyze buffer components

The buffer consists of $\ce{H2CO3}$ (weak acid) and $\ce{NaHCO3}$ (conjugate base, $\ce{HCO3^-}$).

Step 2: Reaction with HCl (a)

HCl is a strong acid, providing $\ce{H^+}$ ions. The conjugate base $\ce{HCO3^-}$ will react with $\ce{H^+}$:
$$\ce{HCO3^- + H^+ -> H2CO3}$$
(From $\ce{HCl -> H^+ + Cl^-}$, so the $\ce{H^+}$ reacts with $\ce{HCO3^-}$ to form $\ce{H2CO3}$)

Step 3: Reaction with NaOH (b)

NaOH is a strong base, providing $\ce{OH^-}$ ions. The weak acid $\ce{H2CO3}$ will react with $\ce{OH^-}$:
$$\ce{H2CO3 + OH^- -> HCO3^- + H2O}$$
(From $\ce{NaOH -> Na^+ + OH^-}$, so the $\ce{OH^-}$ reacts with $\ce{H2CO3}$ to form $\ce{HCO3^-}$ and $\ce{H2O}$)

Answer:

(a) $\boldsymbol{\ce{HCO3^- + H^+ -> H2CO3}}$ (when HCl is added)
(b) $\boldsymbol{\ce{H2CO3 + OH^- -> HCO3^- + H2O}}$ (when NaOH is added)