A covered glass tube contains 2.25g of copper and 3.32g of sulphur. The mass of the tube as well as its contents is 18.48 g. Upon heating a chemical reaction forms copper(II) sulphide (CuS). Each of the copper reacts but only 1.14g of sulphur reacts. Forecast what the mass of the tube and its contents will be after the reaction is completed. Explicate your reasoning.