In which reaction does the oxidation number of hydrogen change? in which reaction does the oxidation number of hydrogen change? 2hclo4 (aq) + caco3 (s) → ca(clo4)2 (aq) + h2o (l) + co2 (g) cao (s) + h2o (l) → ca(oh)2 (s) hcl (aq) + naoh (aq) → nacl (aq) + h2o (l) 2na (s) + 2h2o (l) → 2naoh (aq) + h2 (g) so2 (g) + h2o (l) → h2so3 (aq)

The correct answer is

Explanation:

Oxidation number is defined as the number which is given to an atom when it looses or gains electron. When an atom looses electron, it attains a positive oxidation state. When an atom gains electron, it attains a negative oxidation state.

Oxidation state of the atoms in their elemental state is considered as 0. Hydrogen is present as gaseous state.

For the given chemical reactions:

Oxidation state of hydrogen on reactant side: +1

Oxidation state of hydrogen on product side: +1

Thus, the oxidation state of hydrogen is not changing.

Oxidation state of hydrogen on reactant side: +1

Oxidation state of hydrogen on product side: +1

Thus, the oxidation state of hydrogen is not changing.

Oxidation state of hydrogen on reactant side: +1

Oxidation state of hydrogen on product side: +1

Thus, the oxidation state of hydrogen is not changing.

Oxidation state of hydrogen on reactant side: +1

Oxidation state of hydrogen on product side: 0

Thus, the oxidation state of hydrogen is changing.

Oxidation state of hydrogen on reactant side: +1

Oxidation state of hydrogen on product side: +1

Thus, the oxidation state of hydrogen is not changing.

Hence, the correct answer is