Acetylene (ethyne) burns in oxygen to give carbon dioxide and steam. The balanced reactionis:

A
$C 2 H 2 + 5 O 2 → 4 C O 2 + 2 H 2 O$
B
$2 C 2 H 2 + 3 O 2 → 4 C O 2 + 2 H 2 O$
C
$2 C 2 H 2 + 5 O 2 → 3 C O 2 + 2 H 2 O$
D
$M g (O H) 2 + 2 H C l → M g C l 2 + 2 H 2 O$

Solution:

Concept: A balanced chemical reaction obeys the law of conservation of mass. The total mass of the reactants and the total mass of the products will be equal.
The question is to find the balanced equation. In balanced equations, the number of moles of an element on the reactant side and product side must be equal. This is an outcome of the law of mass conservation. According to the law, matter or mass cannot be created or destroyed. Only one form can be changed to another at a time.
When acetylene,

C 2 H 2

burns with

O 2

carbon dioxide (

C O 2

) and steam (

H 2 O

) is produced. Thus the chemical reaction can be written as

To balance this equation, the number of moles of

C, H

and

O

must be made equal on both sides. Considering carbon, 2 carbon nuclei are present in one mole

C 2 H 2

. In the product, only one

C

nucleus is there in one mole

C O 2

. Thus multiplying moles of

C O 2

by two numbers of carbon can be made equal.

Now consider H atoms, in reactants and products, there are two atoms of hydrogen.
Coming onto

O

atoms, on the reactant side, 2 nuclei of

O

and on the product side a total of 5 O atoms are present. To balance them we can add a coefficient of 5 divided by 2 before

O 2

on the reactant side.

This is a balanced equation. By multiplying with an integer throughout we can form another balanced equation for the same reaction. Now check the given options with the above reaction.

This is the result of the above reaction multiplied throughout by two. Thus this is the balanced equation of acetylene burning in oxygen. So, Option 3 is the correct answer.
Hence, the correct answer is option 3.

Solution:

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