Question

Which coloured entity can be changed to balance the chemical reaction?

• A. Entities in green
• B. Entities in red
• C. Entities in both red and green
• D. None of the colour

Answer 1

The correct option is A

Entities in green

The entities in green and red respectively are called coefficients and subscripts.

Subscripts are the part of the chemical formula of a molecule. They represent the number of atoms in it. Changing these would result in the change in chemical composition of the given molecule which is incorrect. This will result in the representation of an entirely new molecule or a molecule that does not exist. So these should not be changed while balancing chemical reaction.

Example: Consider water, $H_{2}O$, the subscript of hydrogen is 2 and of oxygen is 1, because 1 water molecule contains 2 atoms of hydrogen and 1 atom of oxygen. If subscript of oxygen is changed to 2, i.e., $H_2{O}_2$, this will represent a new compound hydrogen peroxide.

Coefficients represent the number of molecules involved in the chemical reaction. Changing these would not change the chemical composition of the molecule. So only these can be changed to balance a chemical reaction.

Example: $H_{2}O$ represent 1 molecule of water and $2H_{2}O$ represents 2 molecules of water.