When 10 grams of calcium are burned in oxygen 14 grams of calcuim oxide are formed?

The balanced chemical equation for the reaction is:

2Ca + O2 --> 2CaO

This equation shows that for every 2 moles of calcium that react with 1 mole of oxygen, 2 moles of calcium oxide are formed. Since the molar mass of Ca is 40 g/mol, and the molar mass of CaO is 56 g/mol, the 10 grams of calcium would react with 7 grams of oxygen to form 14 grams of calcium oxide.