n NH4Cl = 21,4/53,5 = 0,4 moli
n Ca(OH)2 = 16/74 = 0,216 moli
2NH4Cl + Ca(OH)2 => CaCl2 + 2NH3 + 2H2O
2 moli NH4Cl.................1 mol Ca(OH)2
x moli NH4Cl.................0,216 moli Ca(OH)2
x = 0,432 moli NH4Cl
2 moli NH4Cl.................1 mol Ca(OH)2
0,4 moli NH4Cl.............x = 0,2 moli Ca(OH)2
n Ca(OH)2 exces = 0,216-0,2 = 0,016 moli
m exces = 0,016×74 = 1,2g Ca(OH)2