Question

Two chemicals are available. One is called Sodium Borate Decahydrate and the other is called Aluminum Chloride Hexahydrate. Each can serve as a readily available soucre of water.

Two students attempt to collect water from the hydrates. Lisa uses the Sodium hydrate given, while Michael uses the Aluminum hydrate given in the problem. Lisa uses 437 grams of the Sodium hydrate. That being the case, then determine how many grams of the aluminum hydrate hydrate Michael will have to use if he wishes to obtain the same amount of water collected as Lisa.

Answer 1

1 mole of sodium borate decahydrate (381.38 g) has 10 moles of H2O (10 x 18 = 180 g)

moles of sodium borate decahydrate taken = 437 g/381.38 g/mol = 1.146 mol

moles H2O in sodium borate decahydrate = 10 x 1.146 mol = 11.46 mol H2O

So we need 11.46 moles of H2O from AlCl3.6H2O

1 mole of AlCl3.6H2O (241.432 g) has 6 moles of H2O (6 x 18 = 108 g)

6 moles of H2O in 1 mole of AlCl3.6H2O, so 11.46 mol H2O will be in how much AlCl3.6H2O

so, grams of AlCl3.6H2O needed = 11.46 mol x 241.432 g/mol/6 = 461.135 g, to obtain same amount of water as sodium hydrate.