1. Potassium aluminum sulfate dodecahydrate, KAl(SO4)2·12H2O, is a member of the alum salts. It has a molar mass of 474 g/mol and beautiful solid crystals can be grown from an aqueous solution according to this chemical equation:
The next three questions are based on a synthesis of the alum salt product performed by Kemmi Major. To begin, Kemmi weighs 0.50 g of aluminum metal. She dissolves the aluminum with a strong base to obtain Al3+ cations and adds an excess of the other reactant ions (K+ and SO42-) to the solution. She cools the solution in an ice bath until crystals of alum salt form. What is the theoretical yield of alum product in grams if the reaction works perfectly? (Hint: convert the limiting reactant aluminum to moles of Al. Assume each Al atom gives one Al3+ cation. Use the balanced chemical equation to predict the moles of alum product, and convert this to grams using the molar mass given.) Round the answer to 2 significant digits, with units of g.
2. Kemmi dries her alum crystals and weighs them. Her experimental mass is 6.7 g of alum product from her experiment. What is Kemmi’s percent yield? (Remember, the answer to the previous question is her theoretical yield.) Report 2 significant digits with units of %.
