Find the mass of silicon oxide formed during the decomposition of 300 g

Find the mass of silicon oxide formed during the decomposition of 300 g of potassium silicate, the proportion of impurities in potassium silicate is 15%.

Given:

m (K2SiO3) = 300 g

w% (impurities) = 15%

To find:

m (SiO2) -?

Decision:

K2SiO3 = K2O + SiO2, – we solve the problem, relying on the composed reaction equation:

1) Find the mass of pure potassium silicate:

If the proportion of impurities is 15%, then the proportion of pure substance is 85%,

then m (K2SiO3) = 300 g * 0.85 = 255 g

2) Find the amount of potassium silicate:

n (K2SiO3) = m: M = 255 g: 154 g / mol = 1.65 mol

3) We compose a logical expression:

if 1 mol of K2SiO3 gives 1 mol of SiO2,

then 1.65 mol of K2SiO3 will give x mol of SiO2,

then x = 1.65 mol.

4) Find the mass of silicon oxide obtained during the reaction:

m (SiO2) = n * M = 1.65 mol * 60 g / mol = 99 g.

Answer: m (SiO2) = 99 g.