A)2moles of calcium reacts with 1mole of O2 to form 2moles of calcium oxide. no.of terms of particular element on right side should be equal to left side here it is equal hence the equation is balanced B)1mole of methane reacts with 2moles of O2 to form 2moles of carbondioxide and 2moles of water Solution A)2moles of calcium reacts with 1mole of O2 to form 2moles of calcium oxide. no.of terms of particular element on right side should be equal to left side here it is equal hence the equation is balanced B)1mole of methane reacts with 2moles of O2 to form 2moles of carbondioxide and 2moles of water.