Question

When water is electrolyzed, hydrogen and oxygen are produced in the ratio 2:1. Why?

Answer 1

The mole ratio of hydrogen to oxygen in the water molecule, `"H"_2"O"`, is `2:1`. When water undergoes electrolysis, it decomposes into hydrogen and oxygen gas in a `2:1` ratio.

Explanation:

The chemical equation of the synthesis of water is:

`"2H"_2("g") + "O"_2("g")"` `rarr` `"2H"_2"O("l")"`

We can see from the balanced equation, that the mole ratio of hydrogen to oxygen is `2:1`, both in the water molecule, and in the reactants, hydrogen gas `("H"_2")` and oxygen gas `("O"_2")`.

The electrolysis of water causes the decomposition of water, `"H"_2"O"`, which produces hydrogen and oxygen gas.

The balanced equation is:

`"2H"_2"O("l")` `rarr` `"2H"_2("g") + "O"_2("g")"`

The mole ratio of hydrogen to oxygen is `2:1` in the water molecule, and in the products `"H"_2"` and `"O"_2"` when water decomposes.