Question

When magnesium metal is burned in air (Figure 3.5), two productsare produced. One is magnesium oxide, MgO. The other is the productof the reaction of Mg with molecular nitrogen, magnesium nitride.When water is added to magnesium nitride, it reacts to formmagnesium oxide and ammonia gas.

(a) Based on the charge of the nitride ion (see Table 2.5), predictthe formula of magnesium nitride. (Type your answer using theformat H2O for H2O.)

(b) Write a balanced equation for the reaction of magnesium nitridewith water.
What is the driving force for this reaction?

(c) In an experiment a piece of magnesium ribbon is burned in airin a crucible. The mass of the mixture of MgO and magnesium nitrideafter burning is 0.470 g. Water is added to the crucible, furtherreaction occurs, and the crucible is heated to dryness until thefinal product is 0.486 g of MgO. What was the mass percentage ofmagnesium nitride in the mixture obtained after the initialburning?

(d) Magnesium nitride can also be formed by reaction of the metalwith ammonia at high temperature. Write a balanced equation forthis reaction.
If a 6.3 g Mg ribbon is reacted with 2.57 g NH3(g) and the reactiongoes to completion, which component is the limiting reactant?
What mass of H2(g) is formed in the reaction?

(e) The standard enthalpy of formation of Mg3N2(s) is -461.08 kJmol-1. Calculate the standard enthalpy change for the reactionbetween magnesium metal and ammonia gas.