When carbon is burned in air, it reacts with oxygen to form carbon dioxide. when 20.4 g of carbon were burned in the presence of 66.2 g of oxygen, 11.8 g of oxygen remained unreacted. what mass of carbon dioxide was produced?

74.77 g

The equation for the reaction between carbon and Oxygen is given by;

C(s) + O₂(g) → CO₂(g)

We are given;

Mass of carbon 20.4 g

Mass of Oxygen is 66.2 g

Remaining mass of Oxygen after the reaction is 11.8 g

Therefore, Carbon is the rate limiting reagent since Oxygen was in excess.

We are required to calculate the mass of carbon dioxide produced.

Moles = Mass ÷ Molar mass

Molar mass of carbon = 12.01 g/mol

Therefore;

Moles of Carbon = 20.4 g ÷ 12.01 g/mol

                           = 1.699 moles

From the equation, 1 mole of carbon reacts to produce 1 mole of carbon dioxide.

Therefore, the mole ratio of Carbon to carbon dioxide is 1 :1

Thus, moles of carbon dioxide = Moles of carbon

                                                  = 1.699 moles

Mass = Moles × Molar mass

Molar mass of carbon dioxide = 44.01 g/mol

Therefore;

Mass = 1.699 moles × 44.01 g/mol

         = 74.77 g

Therefore, the mass of carbon dioxide gas produced is 74.77 g

the correct answer is:

a. formation of precipitation