Answer:
C3H8 + 5O2 → 4H2O + 3CO2.
Explanation:
let the balanced equation be A C3H8 + B O2 → C H2O + D CO2.
eqauting carbon hydrogen and oxygen on both sides
we get 3A = D , 8A = 2C, 2B = C + 2D
solving these three equations we get C = 4A and B = 5A
let A = 1
we get B = 5 , C = 4, D=3
therefore the equation becomes
C3H8 + 5O2 → 4H2O + 3CO2.
mass must be conserved on both side of the equation so as to make the reaction possible as energy can neither be created nor be destroyed.