What feature of a chemical equation is used to balance the equation and make sure it obeys the law of conservation of mass?

a
numbers
b
coefficient
c
superscript
d
subscript

b.  Coefficient.

Explanation:

For example:

Zinc combines with oxygen to form zinc oxlde :

We have Zn and O2 forming ZnO:

2Zn + O2 = 2ZnO

The 2's before the Zn and ZnO balance the equation

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).