Chirkut.বাংলা

MCQ practice · SSC Chemistry Board questions · Chapter 7: Chemical Reactions

Dhaka Board 2023

What is the oxidation value of hydrogen in LiAlH₄?

Think it through first, then pick an option.

  1. a + 1
  2. b − 1
  3. c + ½
  4. d − ½
Answer and explanation

Correct answer: b − 1

(+1) + (+3) + 4x = 0 gives x = −1.

Why the other options are wrong

  • a + 1: +1 holds in most compounds; LiAlH₄ is a metal hydride, so H is −1.
  • c + ½: No fraction arises; 4x = −4, so x = −1.
  • d − ½: −½ is for oxygen in a superoxide; H here is −1.

More board questions on this topic