Question

In what ways chemical equation use full to us???

Answer 1

in many ways. for eg when you mix two compounds it will defnitely form a third new compound aand with the help of chemical equation you can know what compound is formed from the reaction
for eg 
C + O2= CO2
thus the equation told me that when i mixed c and oxygen it formed carbon dioxide. Hope this helps

Answer 2

1 It tells us about the amount of reactants and products formed