Question

In order to make modern electronics components, silicon of an extremely high purity is required. One of the steps in purifying silicon involves reacting the intermediate silicon tetrachloride with steam to produce high-purity silicon dioxide and hydrogen chloride gas, as shown in the unbalanced equation below. SiCl4(s) + H2O(g) → SiO2(s) + HCl(g) If the reaction is run with 536.5 g SiCl4 and 103.2 g H2O, what mass of SiO2 will be produced, and what is the excess reactant and what mass of it remains?

(a) What mass of SiO2 will be produced?

(b) What is the excess reactant?

(c) What mass of the excess reactant remains?

Answer 1

SiCl4 MW = 169.9

mol = mass/MW = 536.5/169.9 = 3.15773984697 mol of SiCl4

mol of water = mass/MW = 103.2/18 = 5.7333 mol of H2O

SiCl4(s) + H2O(g) → SiO2(s) + HCl(g)

balance it

SiCl4(s) + 2H2O(g) → SiO2(s) + 4HCl(g)

find limiting reactant

ratio is

1:2

5.7333 mol of H2O will ned 5.7333 /2 = 2.86665 mol of SiCl4 will be needed, which we DO have

thereforeH2O is limiting

then

a)

ratio of 2H2O : SiO2

2*5.7333 = 11.4666 mol of SIO2

mass = mol*MW = 11.4666*60.08 = 688.913328 g will be produced

b)

excess reactant, once again, is SiCl4

c)

mass left:

SiCl4 = 3.15773984697 - 2.86665 =0.29108 mol

mass = mol*wM = 0.29108*169.9 = 49.454492 g left