Chemistry--Unit 5: Stoichiometry
Test Review
vocab
1. actual yield--the amount of product formed when a reaction is carried out in lab
2. excess reactant--a quantity of a reactant that is more than enough to react with a
limiting reactant
3. limiting reactant--the reactant that determines the amount of product that can be
formed in a reaction
4. percent yield--the ratio of the actual yield to the theoretical yield
5. stoichiometry--the calculation of quantities in chemical equations
6. theoretical yield--the calculated amount of product that should be formed during a
reaction
7. titration--a method to determine unknown concentrations of solution from known
concentrations of solutions using the neutralization reaction between acids
and bases
8. equivalence point--when equal moles of acid and base are present during a tritration
and a chosen indicator changes color
Also know what is conserved and not conserved in a reaction
conserved
not conserved
grams, atoms
liters, moles
problems (stoichiometry, limiting reactant, percent yield, titrations)
problems to try
Given the balanced equation Au2S3(s) + 3H2(g)  2Au(s) + 3H2S(g)
1. How many atoms of Au can be obtained from 3.78 x 1024 molecules of Au2S3 ? (7.56
x 1024 atoms Au)
2. How many moles of Au can be obtained from 12 moles of H 2? (8 mol Au)
3. How many grams of H2S are formed if 3.75 moles of Au are formed during a
reaction? (191.7 g H2S)
4. How many moles of H2S can be formed from 36.54 g Au2S3? (0.22 mol H2S)
5. If reactants and products are at the same temperature and pressure, how many liters of
H2 are required to produce 6.97 L of H2S? (6.97 L H2)
Chemistry--Unit 5: Stoichiometry
Test Review
6. At STP, how many grams of Au2S3 are required to produce 6.97 L of H2S? (50.84 g
Au2S3)
7. At STP, how many liters of H2 are required to produce 48.25 g of Au? (8.23 L H2)
8. How many grams of Au can be formed from 35.69 g of Au 2S3 and excess H2? (28.69
g Au)
9. If 4.43 moles of Au2S3 and 16.7 grams of H2 are used in a reaction, how many grams
of Au will form? (1085.96 g)
10. If the reaction in problem 9 was performed in lab and 987.65 g Au were recovered,
calculate the percent yield. (90.95%)
11. Titration reveals that 15.8 mL of 2.00 M sulfuric acid are required to neutralize the
sodium hydroxide in 30.0 mL of NaOH solution. What is the molarity of the NaOH
solution? The titration reaction is H2SO4(aq) + 2NaOH(aq)  Na2SO4(aq) +
2HOH(l). (2.11 M)
12. What volume, in mL, of 0.300 M H3PO4 will be required to neutralize 24 milliliters of
0.250 M KOH? The titration reaction is H3PO4(aq) + 3KOH(aq)  K3PO4(aq) +
3HOH(l). (6.67 mL)
13. What mass, in grams, of KOH will be required to neutralize 100 milliters of 0.800M
HCl? The titration reaction is HCl(aq) + KOH(aq)  KCl(aq) + HOH(l). (4.49
g)