AP Writing Equation Question

For each of the following three reactions, write a balanced equation for the reaction in part (i) and answer the  question about the reaction in part (ii). In part (i), coefficients should be in terms of lowest whole numbers.  Assume that solutions are aqueous unless otherwise indicated. Represent substances in solutions as ions if the substances are extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. You may use the empty space at the bottom of the next page for scratch work, but only equations that are written in the answer boxes provided will be scored.

(a) Solid mercury(II) oxide decomposes as it is heated in an open test tube in a fume hood
            (i) Balanced equation:
 

            (ii) After the reaction is complete, is the mass of the material in the test tube greater than, less than, or equal to the mass of the original sample? Explain.