Question

Water molecule is formed by the reaction,
$2{H_2} + {O_2} \to 2{H_2}O$
What does happen in this reaction?
(A) Electrons are transferred from H to O atom
(B) Electrons are transferred from O to H atom
(C) Electrons are accepted by H from O atom
(D) Electrons are accepted by O to H atom

Answer 1

We know that hydrogen is less electronegative than oxygen. More electronegative elements usually accept electrons from other atoms like hydrogen which are willing to give up their electrons and thus form a more stable configuration. Oxygen will attain a stable noble gas configuration when it gets two more electrons.

Complete answer:
When molecular hydrogen is oxidized by molecular oxygen to form water, the reactions are considered as two coupled processes. Oxygen being highly in need of electrons will get 2 electrons from 2 hydrogen atoms. The hydrogen atom thus loses its electrons. The transfer of electrons from the hydrogen to the oxygen causes reduction of the oxygen and acceptance of electrons from the hydrogen by oxygen causes for the oxidation of the hydrogen.
Thus we can say that when a molecule of water is formed, electrons are transferred from H to O atom.
Thus the correct option is option (A).

Note:
Another method to answer this question is by looking at the oxidation states of the reactants and the products. There is an increase in oxidation number of hydrogen indicating oxidation or loss of electrons and decrease in oxidation number of oxygen indicating reduction or gain of electrons by the oxygen atom.