Question

The hydride ion,${\text{H}}^{-}$is a stronger base than its hydroxide ion, $\text{O}{\text{H}}^{-}$. Which of the following reactions will occur if sodium hydride (NaH) is dissolved in water?
A. ${\text{H}}_{(aq)}^{-}+{\text{H}}_{\text{2}}\text{O}\to {\text{H}}_3{\text{O}}_{(\text{aq)}}^{-}$
B. ${\text{H}}_{(aq)}^{-}+{\text{H}}_{\text{2}}{\text{O}}_{(\text{l)}}\to {\text{OH}}_{\text{(aq)}}^{-}\text{ + }{\text{H}}_{2(\text{g)}}$
C. ${\text{H}}_{(aq)}^{-}+{\text{H}}_{\text{2}}{\text{O}}_{(\text{l)}}\to \text{no reaction}$
D. None of these

Answer 1

Hint:The base reacts with acid and acid reacts with a base. The hydride ion is a strong base, so it will react with an acid. The water can behave as acid or base. How water will behave depends upon the nature of another reacting species.

Complete step-by-step answer:When sodium hydride (NaH) is dissolved in water, sodium hydride dissociates into hydride and sodium ion.
The hydride ion,${\text{H}}^{-}$is a stronger base, so it will abstract a proton from the water. As the water will give protons, so water will work as an acid and an acid-base reaction will take place.
The acid base reaction between water and hydride ion is as follows:
${\text{H}}_{(aq)}^{-}+{\text{H}}_{\text{2}}{\text{O}}_{(\text{l)}}\to {\text{OH}}_{\text{(aq)}}^{-}\text{ + }{\text{H}}_{2(\text{g)}}$
Hydride ions get protons from water and form hydrogen gas and hydroxide ions.
So, because hydride ions are a strong base when sodium hydride (NaH) is dissolved in water, hydrogen gas and hydroxide ion forms.

Additional information: According to the Bronsted-Lowery concept, acids are proton donors and bases are proton acceptors. The acid and base react to form conjugate base and conjugate acid.
Acid forms conjugate base and base forms conjugate acid.
The general reaction of acid and base is shown as follows:
Acid$$+$$Base$\to$ conjugate base$$+$$conjugate acid
In the given reaction, a strong base is hydride ion, a strong acid is water, and weak acid is hydrogen gas weak base is hydroxide ion.

Therefore, option (B) ${\text{H}}_{(aq)}^{-}+{\text{H}}_{\text{2}}{\text{O}}_{(\text{l)}}\to {\text{OH}}_{\text{(aq)}}^{-}\text{ + }{\text{H}}_{2(\text{g)}}$is correct.

Note:The molecule that donates proton is known as acid. Acid accepts electrons. The molecule that accepts protons is known as base. The base donates electrons. The strength of conjugate acid and base depends upon the strength of base and acid. A strong acid or base forms the weak conjugate base or conjugate acid. Weak acid or base forms the strong conjugate base or conjugate acid.