Chemistry reactions

Question

when added to a sealed flask and heated, 6.0g carbon and 16.0g of oxygen react to form 22.0g of carbon dioxide. How much carbon dioxide is formed when 12.0g of carbon is reacted with 100.0g of oxygen?

Answer 1

Two ways to solve this problem using conservation of mass and law of definite proportions, and using stoichiometry.

Notice in the first example, the mass of reactants (6 g + 16 g) is equal to the mass of the products (22 g).  Using the law of definite proportions, you can look at the second situation as follows:

6.0 g C/22.0 g CO₂ = 0.2727 as the fraction that is C

12.0/g22.0g = 0.5455 as the fraction that is O

12 g Carbon/x g CO₂ = 0.2727 and x = 44.0 g CO₂ (Note this is twice as much as in the first experiment.)

So even though there is a lot more oxygen (100g) only 32 g of it will be used and the rest is left over as O₂.

Using stoichiometry:

C + O₂ ==> CO₂

moles C present = 12.0 g x 1 mole/12 g = 1.0 moles

moles O₂ present = 100 g x 1 mole/32 g = 3.125 moles

limiting reactant is C because mole ratio in balanced equation is 1:1

Maximum moles of CO₂ produced = 1.0 moles C x 1 moles CO2/mole C = 1.0 moles CO₂

Mass of CO₂ produced = 1.0 moles CO₂ x 44 g/mole = 44.0 g CO₂