How much air will it take to burn coke weighing 1.92 kg of carbon? (The volume fraction of oxygen in the air is 21%)

Given: m (C) = 1.92 kg; W (O2) = 21%; Find: V (air) =?
Let’s write the formula:
C + O2 = CO2
Find the amount of coke:
n (C2) = 1.92 / 32 = 0.06 mol.
n (C2) = n (O2) since the coefficients are the same
V (O2) = 0.06 * 22.4 = 1.344 l
Now we find the volume of air:
V (air) = (1.344 / 21) * 100 = 6.4 l.
Answer: 6.4 liters of air is needed to burn coke.