Lab Report: The Synthesis Of Alum

Lab report
Experiment 6
The synthesis of Alum
Lingrui Ge
Oct 18th 2015

Purpose: discover the synthesis of alum.
Materials: two 250 mL beakers, 400 mL beaker, 25 mL or 50 Ml GRADUATED cylinder, Buchner funnel and filter flask, watch glass, glass stirring rod, lab burner, ring stand, ring, wire gauze, hot plate, wash acetone, Aluminum foil, 3 M sulfuric acid solution, KOH, 50% enamel solution, ice bath, balance, boiling chips, gloves, pipe cleaner.
Process: get and wear goggles, set up a Buchner funnel and flask and measure its mass. Put the foil into a 250 mL beaker. Get 25 mL of 3M KOH solution, add 5 mL KOH solution into the beaker and stir the beaker. Keep the reaction proceeding until all of the foil is dissolved and use ice bath to make it cool down. Pour the reaction mixture through Buchner funnel and filter flask setup, rinse the filter paper with a small amount of distilled water. Wash the beaker with distilled water and run the rinse solution through the Buchner funnel. Put the filtered liquid back into the beaker, then, clean up the Buchner funnel and filter

Calculate the mass of the isolated alum from the initial mass of the beaker and the mass with the sample.
2. Determine the theoretical yield of the alum in each trial. Use the aluminum foil as the limiting reagent and presume that the foil was pure aluminum.
3. Calculate the percent yield of alum crystals for each trial.
4. Discuss the sources of error that affected the percent yield.
5. Write the balanced net ionic equations for the following reactions:
a. 2 Al(s) + 2 KOH(aq) + 6 H2O(liq) → 2 KAl(OH)4(aq) + 3 H2(g)
b. 2KAl(OH)4(aq) + H2SO4(aq) → 2 Al(OH)3(s) + 2 H2O(liq) + K2SO4(aq), Al(OH)4-(aq) + H+(aq) → Al(OH)3(s) + H2O(liq)
c. 2Al(OH)3(s) + 3 H2SO4(aq) → Al2(SO4)3(aq) + 6 H2O(liq), Al(OH)3(s) + 3 H+(aq) → Al3+(aq) + 3 H2O(liq)
d. Al2(SO4)3(aq) + K2SO4(aq) + 24 H2O(liq) → 2 KAl(SO4)2•12 H2O, K+(aq) + Al3+(aq) + 2 SO42-(aq) + 12 H2O(liq) → KAl(SO4)2•12