Question

You mix 0.901 g of SiO₂ and 0.519 g of C and they react according to the following equation:

SiO₂ + 3 C -> SiC + 2 CO

How many moles of C do you have?

Answer 1

Molar mass of SiO2 = 1*MM(Si) + 2*MM(O)

= 1*28.09 + 2*16.0

= 60.09 g/mol

mass of SiO2 = 0.901 g

we have below equation to be used:

number of mol of SiO2,

n = mass of SiO2/molar mass of SiO2

=(0.901 g)/(60.09 g/mol)

= 1.499*10^-2 mol

Molar mass of C = 12.01 g/mol

mass of C = 0.519 g

we have below equation to be used:

number of mol of C,

n = mass of C/molar mass of C

=(0.519 g)/(12.01 g/mol)

= 4.321*10^-2 mol

we have the Balanced chemical equation as:

SiO2 + 3 C ---> SiC + 2 CO

1 mol of SiO2 reacts with 3 mol of C

for 0.015 mol of SiO2, 0.045 mol of C is required

But we have 0.0432 mol of C

so, C is limiting reagent

we will use C in further calculation

From balanced chemical reaction, we see that

when 3 mol of C reacts, 1 mol of SiO2 is formed

mol of SiO2 reacted = (1/3)* moles of C

= (1/3)*0.0432

= 1.44*10^-2 mol

So,

initially we have 4.321*10^-2 mol of C

after reaction we have 1.44*10^-2 mol of C