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Stoichiometry Problems

For each problem: (1) write the balanced equation, (2) list the given and find, (3) set up the problem using dimensional analysis, (4) calculate the answer to the proper accuracy.

1. How many moles of Pb are formed when 38.2 grams of PbO react according to the following equation:

1 PbS + 2 PbO 3 Pb + 1 SO2?

2. What mass of HF must react to form 23.5 grams of H2O according to the following equation:

1 SiO2 + 4 HF 2 H2O + 1 SiF4?

3. How many moles of NaCl form when 7.4 moles of NaClO react according to the following equation:

3 NaClO 2 NaCl + 1 NaClO3?

4. What volume of O2 gas reacts with 85 grams of As according to the following equation:

4 As + 3 O2 2 As2O3 at STP?

5. How many moles of H2O form when 16.9 liters of N2 gas form according to the following equation:

3 CuO + 2 NH3 3 Cu + 3 H2O + 1 N2 at STP?

6. How many molecules of HCl must react to form 53 grams of AsH3 according to the following:

1 Zn3As2 + 6 HCl 2 AsH3 + 3 ZnCl2?

7. What mass of HI will react with 3.87 liters of O2 gas at STP according to the following unbalanced equation: HI + O2 I2 + H2O?

8. What volume of O2 gas at STP must react to form .68 moles of HgO according to the following unbalanced equation: Hg2O + O2 HgO?

9. How many molecules of AlF3 will form when 25 grams of H2O form according to the following unbalanced equation: Al2O3 + HF AlF3 + H2O?

10. What volume of N2 gas will form when 4.9 liters of O2 gas react according to the following unbalanced equation at STP: NH3 + O2 N2 + H2O?

11. What mass of O2 will react with .638 moles of Fe according to the following unbalanced equation:

Fe + O2 Fe2O3?

12. What mass of P2O5 will react with 56.4 grams of H2O according to the following unbalanced equation:

H2O + P2O5 H3PO4?

13. In the photographic process, silver bromide is dissolved by adding sodium thiosulfate.

AgBr(s) + 2 Na2S2O3(aq) Na3Ag(S2O3)2(aq) + NaBr(aq)

If you want to dissolve 0.125 g of AgBr, how many milliliters of 0.0256 M Na2S2O3 should you add?

14. How many milliliters of 0.250 M HCl would be required to neutralize completely 2.50 g of NaOH?

NaOH(aq) + HCl(aq) NaCl(aq) + H2O([pic])

15. What mass of NH3 will react with 29.1 liters of O2 gas at STP according to the following unbalanced equation: NH3 + O2 N2 + H2O?

16. What volume of O2 gas will react with 8.44 moles of Al at STP according to the following unbalanced equation: Al + O2 Al2O3?

17. What mass of Fe2O3 form when 7.16 grams of H2 forms according to the following unbalanced equation:

Fe + H2O H2 + Fe2O3?

18. What volume of O2 gas must react to form 62 grams of HgO at STP according to the following unbalanced equation: O2 + Hg2O HgO?

19. What volume of O2 gas will form when 3.45 liters of N2 gas react at STP according to the following unbalanced equation: N2 + H2O O2 + NH3?

20. How many moles of O2 form when 30.5 moles of Fe2O3 react according to the following unbalanced equation: Fe2O3 Fe + O2?

21. What volume of N2 gas will react with 15.6 liters of H2 gas at STP according to the following unbalanced equation: N2 + H2 NH3?

22. What mass of Fe will form when 3.9 liters of CO gas react at STP according to the following unbalanced equation: CO + Fe2O3 Fe + CO2?

23. What mass of H2O will form when 81.8 grams of Fe2O3 reacts according to the following unbalanced equation: Fe2O3 + H2 Fe + H2O?

24. What mass of HF must react to form 2.15 moles of AlF3 according to the following unbalanced equation:

HF + Al2O3 AlF3 + H2O?

25. What volume of H2 gas will react with 7.89 liters of O2 gas at STP according to the following unbalanced equation: H2 + O2 H2O?

26. What mass of H3PO4 will form when 136 grams of H2O react according to the following unbalanced equation: H2O + P2O5 H3PO4?

27. What volume of O2 gas will react with 9.55 grams of Hg2O at STP according to the following unbalanced equation: O2 + Hg2O HgO?

28. How many milliliters of 0.0540 M H2SO4 are required to react completely with 1.56 g of KOH?

2 KOH(aq) + H2SO4(aq) 2 H2O([pic]) + K2SO4(aq)

29. Sodium carbonate, Na2CO3, is a good compound to use to standardize acid solutions.

Na2CO3(aq) + 2 HCl(aq) 2 NaCl(aq) + H2O([pic]) + CO2(g)

If 42.43 mL of HCl solution are used to titrate 0.251 g of Na2CO3 to the equivalence point, what is the molar concentration of the acid?

30. What volume of N2 gas reacts when 17 liters of O2 gas form at STP according to the following unbalanced equation: N2 + H2O O2 + NH3?

31. Magnesium chloride reacts with sodium phosphate to produce magnesium phosphate and sodium chloride. If 135 grams of magnesium chloride react, how many grams of sodium chloride form?

32. Zinc reacts with silver nitrate to produce zinc nitrate and silver. If 18.6 grams of zinc react, how many grams of silver form?

33. Chlorine gas reacts with sodium bromide to produce sodium chloride and bromine gas. If 15.9 liters of chlorine gas react at STP, how many grams of sodium chloride form?

34. If apple cider is allowed to spoil, the result is vinegar, the distinctive ingredient of which is acetic acid, CH3COOH. The acid reacts with NaOH according to the balanced equation:

CH3COOH(aq) + NaOH(aq) NaCH3COO(aq) + H2O([pic])

If 25.67. mL of 0.674 M NaOH are required to react completely with a 50.0-mL sample of vinegar, how many grams of acetic acid are in the vinegar sample?

Stoichiometry Problems – Answers

1. .257 moles Pb

2. 52.2 g HF

3. 4.9 moles NaCl

4. 19 liters O2

5. 2.26 moles H2O

6. 1.2 x 1024 molecules HCl

7. 88.4 g HI

8. 3.8 liters O2

9. 5.6 x 1023 molecules AlF3

10. 3.3 liters N2

11. 15.3 g O2

12. 148 g P2O5

13. 52.0 mL

14. 250. mL

15. 29.4 g NH3

16. 142 liters O2

17. 190. g Fe2O3

18. 1.6 liters O2

19. 5.18 liters O2

20. 45.8 moles O2

21. 5.20 liters N2

22. 6.5 g Fe

23. 27.7 g H2O

24. 129 g HF

25. 15.8 liters H2

26. 494 g H3PO4

27. .256 liters O2

28. 258 mL H2SO4

29. .112M

30. 11 liters N2

31. 166 g NaCl

32. 61.4 g Ag

33. 83.0 g NaCl

34. 1.04g acetic acid

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