Theory
What is stoichiometry?
The calculation of quantities in chemical reactions based on balanced equations.
If 6.0 moles of SiO2 react in 3 SiO2 + 4 Al → 3 Si + 2 Al2O3, how many moles of Al react?
8.0 moles
A reaction has a theoretical yield of 12.5 g and an actual yield of 10.0 g. What is the percent yield?
80%
2 H2 + O2 → 2 H2O. Identify limiting reactant: 1.22 g O2 reacts with 1.05 g H2.
O2
2 C₂H₂ + 5 O₂ → 4 CO₂ + 2 H₂O. If 3.0 g of C₂H₂ reacts, how many liters of O₂ are required at STP?
7.6L
Name two reasons why the actual yield is often less than the theoretical yield.
Spillage, incomplete reaction, measurement error, and transfer loss.
How many grams of CO₂ are produced from 5.0 moles of C in the reaction C + O₂ → CO₂?
220.05 g
A reaction produces 12.8 g of NaCl, but theoretical yield is 26.1 g. What is the percent yield?
49%
Mg(OH)2 + 2 HCl → MgCl2 + 2 H2O. Identify limiting reactant: 5.87 g Mg(OH)2 reacts with 12.84 g HCl.
Mg(OH)2
2 K + Br₂ → 2 KBr. If 4.0 g of K reacts with 8.0 g Br₂, which is the limiting reagent?
K
Define “excess reactant.”
The reactant that is not completely used up in a reaction.
If 0.684 moles of C2H2 are produced from 2 C + H2 → C2H2, how many liters of H2 were reacted at STP?
13.6L
FeBr2 + 2 KCl → FeCl2 + 2 KBr. If 34.0 g FeBr2 reacts with excess KCl and actual FeCl2 = 4.0 g, percent yield?
20%
N2O4 + N2H4 → 2 N2 + 2 H2O. Mass of N2 produced if 41.6 g N2O4 reacts with 20.8 g N2H4?
27.3g
Zn + 2 HCl → ZnCl₂ + H₂. If 6.5 g Zn reacts with excess HCl and 2.0 g H₂ is collected, what is the percent yield?
88%
What is a mole ratio?
The ratio of moles of any two substances in a balanced chemical equation, determined by their coefficients.
4 FeS2 + 11 O2 → 2 Fe2O3 + 8 SO2. What mass of Fe2O3 is produced when 25.0 g of FeS2 reacts?
16.6g
2 Hg(NO3)2 → 2 HgO + O2 + 4 NO2. If 83.6 g Hg(NO3)2 reacts and 41.3 g HgO is produced, percent yield?
74%
2 NaI + Cl2 → 2 NaCl + I2. Mass of NaCl produced from 58.7 g NaI + 29.4 g Cl2?
23.5g
2 Na + Cl₂ → 2 NaCl
If 3.0 × 10²³ Cl₂ molecules react with excess Na, how many grams of NaCl are produced?
58.9g
Explain the difference between limiting reagent and theoretical yield.
The limiting reagent is the reactant that runs out first and theoretical yield is the maximum amount of product that could form based on the limiting reagent.
C7H16 + 11 O2 → 7 CO2 + 8 H2O. If 3.9 × 10^23 particles of C7H16 react with 210 g O2, how many grams of CO2 are produced?
180g
If 18.4 g of ZnO is recovered from a reaction where 44.5 g ZnS reacts with 13.3 g O₂, calculate percent yield.
84%
Fe2O3 + 3 CO → 2 Fe + 3 CO2. 1.364 × 10^23 Fe2O3 reacts with 8.784 g CO. Grams of CO2?
16.01g
a. What mass of CS2(s) is produced when 17.5 g of C(s) are reacted with 39.5 g of SO2(g)
according to the equation: 5 C(s) + 2 SO2(g) → CS2(s) + 4 CO(g)?
b. What mass of the excess reactant will be left over?
a) Mass of CS₂ produced = 22.2 g
b) Mass of SO₂ remaining = 2.11 g