Q15 / 160 · AP EAMCET 2020 (18 Sep Shift 1) · Chemistry

The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct? 1. The oxidation number of hydrogen is always +1. 2. The algebraic sum of all the oxidation numbers of all elements in a compound is zero. 3. An element in the free or the uncombined state bears oxidation number zero. 4. In all its compounds, the oxidation number of fluorine is -1.

  • Correct answer
    A
    1
  • B
    2
  • C
    3
  • D
    4

Solution

Oxidation number of hydrogen is usually +1 compounds with more electrongative atoms (as in \(\mathrm{H}_2 \mathrm{O}\)) is +1. But in alkali metal hydride like lithium hydride of the molecule where the oxidation state of hydrogen atom \(=-1\)

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

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