# Question 3b048

Mar 29, 2017

Sodium carbonate is both a salt and a base, but potassium chloride is just a neutral salt.

#### Explanation:

Sodium carbonate

Sodium carbonate is the salt formed by the reaction of carbonic acid with sodium hydroxide.

The equation for the reaction is

$\text{H"_2"CO"_3 + "2NaOH" → "Na"_2"CO"_3 + "2H"_2"O}$

In ionic form, the equation is

underbrace("H"_2"CO"_3)_color(red)("Brønsted acid") + "2OH"^"-" → underbrace("CO"_3^"2-")_color(red)("conjugate base") + "2H"_2"O"#

According to Brønsted-Lowry theory, a weak acid has a stronger conjugate base.

Thus, the carbonate ion is a base because it reacts with water to form hydroxide ion.

$\text{CO"_3^"2-" + "H"_2"O" ⇌ "HCO"_3^"-" + "OH"^"-}$

Potassium chloride

Potassium chloride is the salt formed by the reaction of hydrochloric acid with potassium hydroxide.

The equation for the reaction is

$\text{HCl + KOH" → "KCl" + "H"_2"O}$

In ionic form, the equation is

$\text{H"^"+" + "OH"^"-" → "H"_2"O}$

$\text{HCl}$ is a very strong acid, so its conjugate base $\text{Cl"^"-}$ is a very weak base.

It has no tendency to act as a base in aqueous solution.