Consider the following reactions (not balanced) $\begin{aligned} & \mathrm{BF}_3+\mathrm{NaH} \xrightarrow{450 \mathrm{~K}} \mathrm{X}+\mathrm{NaF} \\ & \mathrm{X}+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Y}+\mathrm{H}_2 \uparrow \end{aligned}$
The correct statements about X and Y are I. X is an electron deficient molecule II. In X, B-B bond is present III. $Y$ is a weak tribasic acid IV. Y acts as a Lewis acid

• Correct answer
  A

  I and IV
• B

  $\amalg$ and III
• C

  II and IV
• D

  I and III

Solution

On balancing the equation (1)
Balancing the equation (2)
X is $\mathrm{BH}_3$ which is an electron deficient molecule. Y is $\mathrm{B}(\mathrm{OH})_3$ which is lewis acid. $\mathrm{B}(\mathrm{OH})_3$ can accept a pair of electron from lewis base.

Hence, the correct answer is option: 'A'.