Question

Why does ammonia act like a base?

(select those that apply)
It combines with H+ions.
Ammonia releases OH-ions.
It increases the OH-concentration.
It dissociates easily.

Answer 1

Answer: It combines with H+ions.

Explanation: It combines with H+ions.

Ammonia releases
`OH^-` ions.

According to Arrhenius concept, a base is defined as a substance which donates hydroxide ions
`(OH^-)` when dissolved in water and an acid is defined as a substance which donates hydronium ions
`(H_3O^+)` in water.

According to the Bronsted Lowry conjugate acid-base theory, an acid is defined as a substance which donates protons and a base is defined as a substance which accepts protons.

According to the Lewis concept, an acid is defined as a substance that accepts electron pairs and base is defined as a substance which donates electron pairs.

`NH_3+H^+\rightarrow NH_4^+`

`NH_4OH(aq)\rightarrow NH_4^++OH^-`

Ammonia being a lewis base donates lone pair of electrons and thus combines with
`H^+`. Also aqueous solution of ammonia gives
`OH^-` ions in water, thus act as Arrhenius base.

Answer 2

Ammonia acts like a base because of these two reasons:
it combines with H+ ions
it increases OH- concentration