Water, <span>rusts a nail faster</span>
The metal car airodinamics with body style and weight increased speed
Balancing of chemical equation is essential because of the law of conservation of mass, which states that the mass of a system can not be created or removed.
The second equation is balanced
This is because the number of elements of each atom in the product side equal the number of elements of each atom on the reactant side.
The first equation is not balanced

This is because there is 1 molecule of
on reactant side as compared to 3 molecules of 
To balance the equation we add a coefficient of 3 on sulphuric acid (
) and a coefficient of 3 on hydrogen (
)

Phosphoric acid. Also known as orthophosphoric acid in or phosphoric(V) acid, is a weak acid with the chemical formula H3PO4. The pure compound is a colorless solid.
The number of oxygen atoms are 6 atoms
<u><em>Explanation</em></u>
According to the law of mass conservation the number of reactant atoms is equal to number of product atoms.
For given equation to obey the law of mass conservation it need to be balanced as below
4 Al + 3 O₂ → 2 Al₂O₃
Al₂O₃ is the product,therefore the number of oxygen atom
= coefficient in front of Al₂O₃ × subscript of O
=2 x 3 = 6 atoms