The correct option is this: 2C4H10 + 2Cl2 + 12O2 = 7CO2 + CCl4 + 10H2O
The law of conservation of mass states that matter can neither be created nor destroyed. In chemical equations, this law implies that, the number of molecules and atoms that are found in reactants must always be equal to those found in products formed. Looking at the chemical equations given above, one will observe that it is only the one given in option A that has the same number of atoms on both side of the equations, all other equations are not balanced. For options A, at the reactant side, there are 8 atoms of carbon, 20 atoms of hydrogen, 4 atoms of chlorine and 24 atoms of oxygen and these are the same numbers that are found on the product side.
