In the balanced equation
2C₂H6+702--> 4CO2+6H₂O
if 21 g of C₂H6 react with 32 g O2, what is the limiting reactant?
02
C₂H6
CO₂
H₂O
To determine the limiting reactant, we need to calculate how much CO2 and H2O each reactant can produce based on their given masses and stoichiometry.
For C2H6:
Molar mass of C2H6 = 2(12.01) + 6(1.01) = 30.07 g/mol
Number of moles of C2H6 = 21 g / 30.07 g/mol = 0.70 mol
From the balanced equation, 2 moles of C2H6 can produce 4 moles of CO2
Moles of CO2 that can be produced = 2/2 x 0.70 mol = 1.40 mol
From the balanced equation, 2 moles of C2H6 can produce 6 moles of H2O
Moles of H2O that can be produced = 2/2 x 0.70 mol = 1.40 mol
For O2:
Molar mass of O2 = 2(16.00) = 32.00 g/mol
Number of moles of O2 = 32 g / 32.00 g/mol = 1.00 mol
From the balanced equation, 1 mole of O2 can produce 2 moles of CO2
Moles of CO2 that can be produced = 2/7 x 1.00 mol = 0.29 mol
From the balanced equation, 1 mole of O2 can produce 3 moles of H2O
Moles of H2O that can be produced = 3/7 x 1.00 mol = 0.43 mol
Since O2 can only produce 0.29 mol of CO2 while C2H6 can produce 1.40 mol of CO2, O2 is the limiting reactant. Therefore, it will limit the amount of CO2 and H2O that can be produced in the reaction.
To determine the limiting reactant, we need to compare the number of moles of each reactant to the stoichiometric ratio in the balanced equation.
1. Start by calculating the number of moles for each reactant:
The molar mass of C₂H6 (ethane) is 30.07 g/mol.
The molar mass of O2 (oxygen gas) is 32.00 g/mol.
Number of moles of C₂H6 = Mass of C₂H6 / Molar mass of C₂H6
= 21 g / 30.07 g/mol
≈ 0.699 mol
Number of moles of O2 = Mass of O2 / Molar mass of O2
= 32 g / 32.00 g/mol
= 1 mol
2. Next, compare the moles of each reactant to the stoichiometric ratio in the balanced equation:
From the balanced equation, the stoichiometric ratio between C₂H6 and O2 is 2:7. This means that for every 2 moles of C₂H6, we need 7 moles of O2.
Number of moles of O2 / stoichiometric coefficient of O2 = 1 mol / 7 = 0.143 mol
Number of moles of C₂H6 / stoichiometric coefficient of C₂H6 = 0.699 mol / 2 = 0.349 mol
3. The reactant that produces fewer moles of product is the limiting reactant. In this case, C₂H6 produces fewer moles of product compared to O2. Therefore, the limiting reactant is C₂H6.