Question

When hydrogen burns in oxygen, water is formed, when
clectricity is passed through water, hydrogen and oxygen
are given out. Name the type of chemical changes involved
in the two cases.​

Answer 1

For first reaction :-

It is given that hydrogen gas is burning in oxygen and forming water .

So, the balanced chemical equation for the reaction is :-

2H₂ + O₂ → 2H₂O

In this case, we can clearly see that hydrogen and oxygen are combining to give water. So, it is a combination reaction .

For 2nd reaction :-

In this case, electricity is passed through water and hydrogen and oxygen gas are given out .

So, the balanced chemical equation will be :-

2H₂O → 2H₂ + O₂

Here, water is getting decomposed by electrolysis and giving two products i.e. hydrogen and oxygen. So, it is a decomposition reaction .

Some Extra Information :-

• In a combination reaction, two or more substances combine to form a new single substance .

• In a decompostion reaction, opposite thing occurs . A single substance decomposes to give two or more substances .

Answer 2

Required Answer :-

1]

Formula of water = H₂O

Equation - 2H₂ + O₂ ⇒ 2H₂O

Type - Combination

As combination reaction defines that two or more element combine to form a single compound or mixture. Here, the same case is happening

2]

2H₂O ⇒ 2H₂ + O₂

Type - Decomposition reaction

As deconposition reaction defines that the elements changed their place with other one. Here, same thing is happening.

Rule - If AB and CD are two element then

AB + CD → CB + DA is a decomposition reaction