Question

Many computer chips are manufactured from silicon, which occurs in nature as SiO2. When SiO2 is heated to melting, it reacts with solid carbon to form liquid silicon and carbon monoxide gas. In an industrial preparation of silicon, 156.1 kg of SiO2 is allowed to react with 78.5 kg of carbon to produce 66.2 kg of silicon.

Determine the theoretical yield for the reaction.

Answer 1

Solution :-

Balanced reaction equation

SiO2(l) + 2C(s) ---- > 2CO(g) + Si(l)

mass of SiO2 = 156.1 kg

mass of C= 78.5 kg

Theoretical yield = ?

To calculae the threoretical yield we need to use the mole ratio of the both reactants and calculate the mass of the product formed.

calculating the mass of Si produced from the 156.1 kg SiO2

(156.1 kg SiO2 * 1000 g / 1 kg) *(1 mol SiO2/60.084 g)*(1 mol Si/1 mol SiO2)*(28.086 g/1mol Si)*(1 kg/1000g) =72.97 kg Si

now lets calculate the mass of Si produced from the 78.5 kg C

(78.5 kg C*1000g/1kg)*(1 mol C / 12.01 g)*(1mol Si / 2 mol C)*(28.086 g/1mol Si)*(1 kg/1000g) = 91.79 kg Si

The mass of the Si produced from the SiO2 is less than it produced from the C

therefore the SiO2 is the limiting reactant

Therefore theoretical mass of the Si(l) = 72.97 kg