Question

Magnesium powder reacts with steam to form magnesium hydroxide and hydrogen gas.
a) Write a balanced chemical equation for this reaction.
b) What is the percentage yield if 10.1g Mg reacts with an excess of water and 21.0g Mg(OH)2 is recovered?
c) If 24g Mg is used and the percentage yield is 95%, how many grams of magnesium hydroxide should be recovered?

Answer 1

a) Mg + 2H2O ==> Mg(OH)2 + H2

Answer 2

The equation by Jake is correct. Here is a solved example for stoichiometry problems as well as percent yield. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html

Answer 3

For the reaction shown, calculate how many grams of oxygen form when each quantity of reactant completely reacts.
2HgO(s)→2Hg(l)+O2(g)