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MOLE CONVERSION PROBLEMS
1. What is the molar mass of MgO? [40.31 g/mol]
2. How many moles are present in 34 grams of Cu(OH)2? [0.35 moles]
3. How many moles are present in 2.5 x 1023 molecules of CH4? [0.42 moles]
4. How many grams are there in 3.4 x 1024 molecules of NH3? [96 grams]
5. How much does 4.20 moles of Ca(NO3)2 weigh? [689 grams]
6. How many molecules are there in 24.0 grams of FeF3? [1.28 x 1023 molecules]
7. How many molecules are there in 450. grams of Na2SO4? [1.91 x 1024 molecules]
8. How many grams are there in 2.30 x 1024 atoms of silver? [412 grams]
9. How many grams are there in 7.40 x 1023 molecules of AgNO3? [209 grams]
10. How many grams are there in 7.50 x 1023 molecules of H2SO4? [122 grams]
11. How many molecules are there in 122 grams of Cu(NO3)2? [3.92 x 1023 molecules]
12. How many grams are there in 9.40 x 1025 molecules of H2? [315 grams]
13. How many moles of oxygen atoms are there in 20.3 grams of NH4SO2? [0.495 moles]
14. How many grams are there in 3.30 x 1023 molecules of N2I6? [433 grams]
15. How many molecules are there in 201 grams of CCl4? [7.87 x 1023 molecules]
16. How many grams are there in 1.00 x 1024 molecules of BCl3? [195 grams]
17. How many grams are there in 4.50 x 1022 molecules of Ba(NO2)2? [17.1 grams]
18. How many molecules are there in 9.34 grams of LiCl? [1.33 x 1023 molecules]
19. How many grams do 4.31 x 1023 molecules of UF6 weigh? [251 grams]
20. How many molecules are there in 232 grams of NH4OH? [3.99 x 1024 molecules]
And the Mole goes on…
PART A: EMPIRICAL AND MOLECULAR FORMULAS
21. Determine the empirical formula of a compound that contains 58.84% barium, 13.74%
sulfur, and 27.42% oxygen by mass. [BaSO4]
22. What is the empirical formula of a compound that has 66% Calcium and 34%
Phosphorous? [Ca3P2]
23. Find the empirical formula of a compound that is 48.38% carbon, 8.12% hydrogen, and
53.5% oxygen by mass. What is the molecular formula of this compound if the
molecular mass is 328.36 g/mol [C6H12O5, C12H24O10]
24. An organic compound has an empirical formula of CH3 and a molecular mass of 30.08 u. What is the molecular formula? [C2H6]
PART B: MOLE RATIOS
1. How many moles of carbon will be produced when 0.214 moles of oxygen gas reacts
with excess C2H6 gas to form carbon and water?
(0.285 moles)
2. What is the mass of water will be produced when 14.2 moles of CH4 react with excess
oxygen gas to form carbon dioxide and water?
(512 grams)
3. How many moles of ammonia will be produced when 18.6 moles of hydrogen gas reacts
with excess nitrogen gas?
(12.4 moles)
4. What is the mass of hydrogen gas would be needed if 18.0 moles of ammonia are
produced from a reaction between hydrogen and nitrogen gas? (54.5 grams)
5. What mass of nitrogen gas would be needed if 0.921 moles of ammonia are produced
from a reaction between hydrogen and nitrogen gas?
(12.9 grams)
6. What mass of ammonia would be produced if 15.0 moles of hydrogen gas reacts with
22.0 moles of nitrogen gas?
(170. grams)
GRAVIMETRIC STOICHIOMETRY PROBLEMS
1. What mass of oxygen will be produced by heating 400. g of potassium chlorate?
2 KClO3 → 2 KCl + 3 O2
2. What mass of ferrous sulphide will be produced by the reaction of 160. g of iron with
excess sulphur?
8 Fe + S8 → 8 FeS
3. How many g of copper (II) sulphate can be made from 100. g of copper(II) sulphate
pentahydrate?
CuSO4 • 5H2O → CuSO4 + 5 H2O
4. How many grams of chlorine could be obtained by heating 70. g of manganese dioxide
with an excess of hydrochloric acid?
MnO2 + 4 HCl → MnCl2 + 2 H2O + Cl2
5. What mass of iron (II) sulfide must be burned in air to produce 400. g of iron(III) oxide?
4 FeS + 11 O2 → 2 Fe2O3 + 8 SO2
6. Calculate the mass of magnesium oxide formed by the burning of 55 g of magnesium?
2 Mg + O2 → 2 MgO
7. What mass of sulphur dioxide can be formed when 64 g of sulphur are burned?
S8 + 8 O2 → 8 SO2
How many grams of hydrogen are produced by the action of 30. g of zinc with excess
sulphuric acid?
Zn + H2SO4 → ZnSO4 + H2
Limiting Reagent Practice Problems
1) At high temperatures, sulphur combines with iron to form iron (II) sulphide. In one experiment, 7.62
grams of Fe are allowed to react with 8.67 grams of S.
a) What is the limiting reagent and what is the reactant in excess?
b) Calculate the mass of FeS that can be formed
2) Zinc metal reacts with hydrochloric acid to produce zinc chloride and hydrogen gas. A 3.50 g sample of
zinc metal is allowed to react with 2.50 grams of hydrochloric acid. Complete the following table:
Reactants/Products Zn (grams)
HCl (grams)
ZnCl2 (grams)
H2 (grams)
Before reaction
2.50 grams
0.00 grams
0.00 grams
3.50 grams
After reaction
Is the law of conservation of mass obeyed in this question?
3) Chlorine gas reacts with silica (SiO2) and carbon to give silicon tetrachloride and carbon monoxide. Be
sure to write out a balanced chemical equation. How much CO gas can be produced from 50.0 grams
of chlorine gas, 15.0 grams of silica, and 13.0 grams of carbon? (Hint: Find the limiting reagent!)
4) When iron (II) hydroxide is mixed with phosphoric acid, iron (II) phosphate is produced.
a) If 3.20 grams of Fe(OH)2 is treated with 2.50 grams of phosphoric acid, what is the limiting reagent?
b) How many grams of iron (II) phosphate would be produced?
Numerical Answers
1)
Fe is limiting reagent, S is in excess, 12.2 grams of FeS are formed
2)
After reaction: 1.26 grams of Zn, 0.00 grams of HCl, 4.67 grams of ZnCl2, and 0.069 grams of H2.
Mass of reactants used is equal to mass of products. Law of conservation of mass is upheld.
3)
14.0 grams of CO are produced
4)
Iron (II) hydroxide is the limiting reagent and 4.24 grams of iron (II) phosphate would be produced
QUANTITIES IN CHEMICAL REACTIONS UNIT REVIEW
1. Calculate the relative atomic mass for Neon given that its isotopic composition is 90.92% 20Ne,
0.26% 21Ne and 8.82% 22Ne. (20.18 u)
2. How many moles of Ba ions are found in 107.5 g of Ba(ClO3)2 ? (0.3534 mol)
3. What is the mass in grams of two moles of CCl4? (307.62 g)
4. How many molecules of CO2 are found in 6.35 g? (8.69 x 1022 molecules)
5. Calculate the simplest formula for a compound found to be 26.57 %K, 35.36 % Cr and 38.07 % O.
(K2Cr2O7)
6. What mass of copper would be required to react completely with 250. g of nitric acid? (94.5 g)
a. 3 Cu + 8 HNO3 → 3 Cu(NO3) 2 + 4 H2O + 2 NO
7. What mass of hydrogen is needed to reduce 4.6 g of ferric oxide to iron and water?
(0.17 g)
8. What mass of hydrogen is produced when 15.0 t of ore containing 0.100% of zinc reacts with excess
sulphuric acid? (1t = 1 000 000 g )
(463 g)
One type of stomach antacid "Tum-Ez" consists of 80% magnesium hydroxide, Mg(OH)2.
This reacts with stomach acid, which is mainly hydrochloric acid, as follows
Mg(OH)2(aq) + 2 HCl(aq) → MgCl2(aq) + 2 H2O(l)
If 2.15 g of Tum-Ez (2 tablets) is available for reaction with 1.52 g of hydrochloric acid, will all the
hydrochloric acid be neutralized?
(Yes, all HCl will be neutralized)
10. If 36.0 g of sodium hydroxide reacts with 12.0 g of phosphoric acid, what mass of Na3PO4 will be
produced? (20.0 g)
11. One type of stomach antacid consists of magnesium hydroxide, Mg(OH)2. This reacts with stomach
acid, which is mainly hydrochloric acid, as follows:
Mg(OH)2(aq) + 2 HCl(aq)
→ MgCl2(aq)
+ 2 H2O(l)
a) If 2.86 g of magnesium hydroxide and 1.5 g of hydrochloric acid are available for reaction, what
mass of magnesium chloride will be produced? (1.96 g)
b) Calculate the % yield if 1.78 g of product is obtained. (90.8%)