When hydrogen reacts with calcium metal, what are the oxidation numbers of the calcium and hydrogen in the CaH2 product? Ca(s)+ H2(g) → CaH2

a. +2 and -1
b. +1 and -2
c. +2 and 2
d. 0 and 0
e. -2 and +1

The oxidation number of calcium has been +2, and the oxidation number of hydrogen has been -1. Thus, the correct option is A.

The oxidation number can be defined as the number of electrons that have been lost by an atom in a chemical reaction.

The oxidation number can be calculated as the:

The oxidation number of Hydrogen when it combines with the less electronegative element has been -1.

There have been 2 atoms of Hydrogen that lose an electron, thus the total oxidation contribution of hydrogen has been -2.

The oxidation number of hydrogen has been -1.

The oxidation number of Calcium has been:

Ca atom has taken an electron from the hydrogen.

The calcium takes one electron from each atom bonded. Thus the oxidation number of calcium has been +2.

The oxidation number of calcium has been +2, and the oxidation number of hydrogen has been -1. Thus, the correct option is A.

For more information about oxidation numbers, refer to the link:

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 e. -2 and +1

Explanation:

Oxidation number or oxidation state : It represent the number of electrons lost or gained by the atoms of an element in a compound.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation number of the substance increases.

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation number of the substance gets reduced.

The oxidation number of calcium (Ca) in free state is 0 and in , it is -2.

The oxidation number of hydrogen in is zero and oxidation number of hydrogen in  is +1 as in hydrides hydrogen loses electrons.