To 36 g of a 20% solution of barium chloride was added 20 g of a 10% solution

To 36 g of a 20% solution of barium chloride was added 20 g of a 10% solution of potassium sulfate. Calculate the mass of precipitated sediment.

Given:

m (BaCl2) = 36 g

m (K2SO4) = 20g

w% (BaCl2) = 20%

w% (K2SO4) = 10%

To find:

m (draft) -?

Decision:

BaCl2 + K2SO4 = 2KCl + BaSO4, – we solve the problem, relying on the composed reaction equation:

1) Find the masses of barium chloride and potassium sulfate in solutions:

m (BaCl2) = 36 g * 0.2 = 7.2 g

m (K2SO4) = 20 g * 0.1 = 2 g

2) Find the amount of barium chloride and potassium sulfate:

n (BaCl2) = m: M = 7.2 g: 208 g / mol = 0.035 mol

n (K2SO4) = m: M = 2 g: 174 g / mol = 0.0115 mol

We start from a lower value to get more accurate calculations. We work with K2SO4:

3) We compose a logical expression:

if 1 mol of K2SO4 gives 1 mol of BaSO4,

then 0.0115 mol of K2SO4 will give x mol of BaSO4,

then x = 0.0115 mol.

4) Find the mass of barium sulfate precipitated:

m (BaSO4) = n * M = 0.0115 mol * 233 g / mol = 2.68 g.

Answer: m (BaSO4) = 2.68 g.