Question

Part A... Barium can be analyzed by precipitating it as BaSO4 and weighing the precipitate. When a 0.255 g sample of a barium compound was treated with excess H2SO4 8.90×10−2 g of BaSO4 formed. What is the percentage of barium in the compound?

Part B.. What is the percentage of sodium in pure table salt? Report your answer as a pecenteage to three significant figures.

Part C.. An impure sample of table salt that weighed 0.8791 g when dissolved in water and treated with excess AgNO3 formed 2.029 g of AgCl . What percentage of NaCl is in the impure sample?

Answer 1

A)

mol of BaSO4 = mass/MW = (8.9*10^-2) /(233.3896) = 0.00038 mol of BaSO4 = 0.00038mol of Ba2+

then

mol of Ba copmound = 0.00038

mass of Ba = 0.00038*137.327 = 0.05218 g

% Ba = mass of ba / Total mass * 100% = 0.05218/0.255*100 = 20.462%

b)

% Sodium in NaCl -->

% Na = mas sof Na / total mass * 100% = 23/58.5*100 = 39.31 %

c)

mol of AgCl = mass/MW = 2.029/143.32 = 0.0141

mol fo cL- = 0.0141

mol of NaCl = 0.0141

mass = mol*MW = 0.0141*58.5 = 0.82485 g of NaCl

% Nacl = 0.82485/0.8791 *100 = 93.8%