limiting & excess. cookie stoichiometry to make one batch, it requires: 2 eggs 2 cups of flour...
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Cookie Stoichiometry• To make one batch,
it requires:• 2 eggs• 2 cups of flour• 2/3 cups of butter
• How many batches could you make with…– 4 eggs– 6 cups of flour– 2/3 cups of butter
– The cups of butter was your limiting reagent– The eggs and flour were your excess reagents– But how could you show this
mathematically…?
Example 1
20.00 g of H2 react with 100.0 g of O2 according to the reaction
2 H2 + O2 2 H2O
Which reactant is limiting and which reactant is in excess?
Example 1
1. Calculate the number of moles of a product formed.
Mole of H2O (based on
H2)=
20.00 g H2
x
1 mol H2
x
2 mol H2O
=10.0 mole
H2O2.0 g H2 2 mol H2
Mole of H2O (based on O2)
= 100.0 g O2 x1 mol O2
x2 mol H2O
=6.25 mol H2O
32.0 g O2 1 mol O2
Example 1
Determine the limiting and excess reactants.
O2 is the limiting reactant.
H2 is the excess reactant.
2. How much H2 (in grams) is left after O2 runs out?
Example 1
3. To find mass of H2 in excess, find the mass of H2 which will react based on the mass of the limiting reactant.Mass of H2
(based on O2)= 100.0 g O2 x
1 mol O2x
2 mol H2x
2.0 g H2=
12.5 g H232.0 g O2 1 mol O2 1 mol H2
Example 1
4. Then, subtract the mass of H2 which reacts from the starting mass of H2.
Mass of H2 (in excess)
= mass H2 (at start) – mass H2 (reacted)
= 20.00 g – 12.5g = 7.5 g
Take Attendance
Example 2
If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction
FeCl2 + KNO3 + HCl FeCl3 + NO + H2O + KCl
a) What is the limiting reactant?
b) How many grams of each “excess” reactant left in the reaction vessel?
Example 2
If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction
3 FeCl2 + KNO3 + 4 HCl 3 FeCl3 + NO + 2 H2O + KCl
a) What is the limiting reactant?
b) How many grams of each “excess” reactant left in the reaction vessel?
Example 2
If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction
3 FeCl2 + KNO3 + 4 HCl 3 FeCl3 + NO + 2 H2O + KCl
a) What is the limiting reactant? KNO3
b) How many grams of each “excess” reactant left in the reaction vessel?
Example 2
If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction
3 FeCl2 + KNO3 + 4 HCl 3 FeCl3 + NO + 2 H2O + KCl
a) What is the limiting reactant? KNO3
b) b) How many grams of each “excess” reactant are actually present in excess? FeCl2 = 0.8g, HCl = 18.5g
Example 3
If 3.2 g of CuSO4, 2.5 g of water and 3.0 g of SO2 are reacted together in the reaction:
CuSO4 + H2O + SO2 Cu + H2SO4
• Which reactant is the limiting reactant?• What is the mass of each of the excess reactants?
Example 4
700. mL of 0.350 M ammonia (NH3) solution is mixed with 15.0 g of solid magnesium to produce magnesium nitride and hydrogen gas.• Which reactant is in excess?• How much (in grams) of the excess reactant
remains after the reaction is complete?
Example 5:
For the reaction:
TiO2(aq) + B4C(g) + C(s) TiB2(aq) + CO(g)
If 11.5 L of 0.800 M TiO2, 455 g of solid carbon and 184 L of B4C gas at STP react together. Find the amount (based on the original units given) of the reactants left over.
Example 5:
For the reaction:
2TiO2(aq) + B4C(g) + 3 C(s) 2TiB2(aq) + 4CO(g)
If 11.5 L of 0.800 M TiO2, 455 g of solid carbon and 184 L of B4C gas at STP react together. Find the amount (based on the original units given) of the reactants left over.