Chemistry I – Unit 4, Chemical Quantities

Chapter 10 - Chemical Quantities

Section / Pages / Problems
10.1- The Mole: A measurement of matter / 287 – 296 / p. 296 # 13, 14, 15
10.2- Mole-Mass and Mole-Volume relationships / 297 – 299 / p. 303 # 26, 27
10.3- Percent composition and chemical formulas / 305 – 312 / p. 312 # 42, 43, 44, 45, 46
Review / 315 / # 49, 50, 53 a, b, c, 58 a, b, 59 e, f, 63 a, d, 66, 68 b, 80


CALCULATION OF MOLAR MASS

Determine the quantity (number) of each atom in the following compounds: NAME THE COMPOUNDS

CCl4 Al(NO3)3 Ca3(PO4)2

Fe3N2 KC2H3O2 Mg(HCO3)2

Find the molar mass for each of the following compounds: NAME THE COMPOUNDS

C3H8 Na2SO4 KMnO4

Fe2O3 (NH4)2SO4 Co2(SO4)3

Mole Practice

Calculate the number of moles for the following compounds. Name the compound!

1) 12.34 g of K3PO4 / 2) 3.400 g of NO2
3) 150.5 g of CCl4 / 4) 0.87 g of AgNO3

Calculate the number of grams for the following compounds. Write the chemical formula!

1) 3.40 mol of ammonium acetate / 2) 0.89 mol of lithium bromide
3) 0.00123 mol of diphosphorus pentoxide / 4) 18.7 mol of aluminum oxide

Calculate the number of molecules from the number of moles: WRITE THE NAME!

1) 6.78 mol of SO3 / 2) 10.89 mol of K2CO3
3) 0.00153 mol of AgNO3 / 4) 9.7 mol of Fe2O3

Calculate the number of molecules from the each of these. Be sure to write the chemical formula!

1) 4.56 g of magnesium chloride / 2) 8.7 g of water
3) 0.431 g of iron (III)bromide / 4) 2.12 g of zinc sulfate

PERCENTAGE COMPOSITION

Calculate the percentage composition of each element in the following compounds: NAME EACH COMPOUND that is not already named.

1) PbS / 5) MoS2
2) HgS / 6) Cu2O
3) WO / 7) Acetaminophen C8H9NO2
4) Aspirin C9H8O4 / 8) CuSO4


Empirical Formula Problems

1. Give the empirical formula that corresponds to the following molecular formula:

a) Na2O2 b) C8H6O4 c) C12H12N2O3 d) C6H12O6

2. A compound is found to have the following weight composition: carbon, 92.3%; hydrogen, 7.7%. Calculate its simplest OR empirical formula.

3. A sulfur compound contains 50% sulfur and 50% oxygen. What is its simplest (empirical) formula?

4. A compound contains 0.21g of hydrogen, 3.26 g of sulfur, and 6.53 g of oxygen. What is its empirical formula?

5. Ascorbic acid is another name for Vitamin C. It is composed of 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen, by mass. Determine the empirical formula for ascorbic acid.

From the following weight compositions, calculate simplest or empirical formulas:

6. potassium = 24.68%, manganese = 34.81%, oxygen = 40.51%

7. potassium = 28.15%, chlorine = 25.63%, oxygen = 46.22%

8. sodium = 42.07%, phosphorus = 18.91%, oxygen = 39.02%

9. In an experiment, a 2.541 g sample of calcium was heated in a stream of pure oxygen, and was found to increase in mass by 1.004 g. Calculate the empirical formula of the calcium oxide.

10. If a 1.271 g sample of aluminum metal is heated in a chlorine gas atmosphere, the mass of aluminum chloride produced is 6.280 g. Calculate the empirical formula of aluminum chloride.

11. Analysis of a sample of vanadium oxide revealed 1.91 grams of vanadium and 1.50 grams of oxygen. Calculate its simplest formula.

12. When 1.35 grams of silver oxide are decomposed, there remains a silver residue of 1.26 grams. Calculate the simplest formula of silver oxide.

Empirical formula of hydrates:

Determine the number of waters of hydration (or mole ratio of water to compound) in the following hydrates:

13. washing soda: Na2CO3 = 37.07%, H20 = 62.93% (what is its proper name?)

14. Glauber's salt: Na2SO4 = 44.10%, H20 = 55.90% (name?)

15. borax: Na2B407 = 52.7%, H20 = 47.3%

16. What is the % water in CuSO4× 5H2O

17. What is the % water in MgSO4 × 12H2O

MOLECULAR FORMULA

18. A compound with the empirical formula CH2O was found to have a molar mass of 90 g/mol. What is the molecular formula?

19. A compound with the empirical formula of CH4O was found in subsequent experiment to have a molar mass of approximately 192 g/mol. What is the molecular formula of the compound?

20. A compound, with a known molar mass of 28.1 g/mol, contains 85.7 1 % carbon and 14.29% hydrogen. Calculate its correct molecular formula.

21. A sample of a compound is found to contain 0.97 grams of phosphorus and 1.25 grams of oxygen. Its correct molar mass is 284.0 g/mol. Calculate its correct molecular formula.

22. Hydrazine, a high-energy fuel, is found to contain 87.5% nitrogen and 12.5% hydrogen. Calculate its simplest formula. Its correct molecular weight is 32 g/mol. What is its correct molecular fomula?

23. A sample of calcium carbide is analyzed and found to contain 62.5% calcium and 37.5% carbon. What is its simplest formula? If the correct formula weight is 64 g/mol, what is its correct formula?

REVIEW:

1) How many protons, neutrons, and electrons in the following:

a.  U-232 b. C-10 c. Ti-50

2) Write the formula for the following compounds:

a.  Dinitrogen tetroxide

b.  Sodium cyanide

c.  Aluminum sulfate

d.  Iodine pentafluoride

3) The density of lead is 11.35 g/mL. In an experiment a student fills a graduated cylinder will 5.67 mL of water. She then places some lead beads in the cylinder and the new volume is 8.12 mL. How many moles of lead did she place in the cylinder? How many atoms of lead?

4) Given the following data shown in the graph below determine the density of the substance. If you had 6.0 grams of the substance, what would be its volume?

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