Chapter 8 Chemical Quantities
Molecular Weight and Moles
Find the molecular mass or formula massof each of the following
1. HNO3
3. Fe2O3
5. H3PO4
2. Ammonium nitrate
4. Rubidium Sulfite
6. Lithium Carbonate
7. K2SO4
8. Magnesium Hydroxide
9. Be5As2
10. Aluminum Sulfate
Find the mass of each of the following expressed in grams
11. 1.0 mol of HC2H3O2
12. 0.23 mol of sodium acetate
13. 2.5 mol of K2CrO4
14. 0.572 g of calcium phosphate
15. 0.50 mol of Ca(ClO3)
16. 0.0582 mol lithium sulfate
17. 0.25mol of Ba(NO3)2
18. 0.418 mol of iron (II) nitrate
19. 0.375 mol of Na2Cr2O7
20. 1.872 mol copper (II) acetate
Find the mass of each of the following, expressed in moles
21. 100.0g of CaCO3
22.
3.5 g of arsenic trichloride
23. 100.0g of Ni(NO3)2
24.
0.572g of calcium phosphide
25. 50.0g of C6H12O6
26.
1.75g of calcium acetate
27. 25.0g K3PO4
28.
4.904g of aluminum nitrate
29. 15.57g of Bi(OH)3
30.
27.85g of iron(II)phosphate
Calculate grams for each of the following
31. 6.02 x 1023 atoms of Na
32.
3.01 x 1023 ions on NaOH
33. 12.04 x1023 atoms of Ca
34.
1.505 x 1023 ions Na+
35. 3.01 x 1023 atoms of S
36.
24.08 x 1023 molecules H2O
H. Cannon, C. Clapper and T. Guillot
Klein High School
Chemical Quantities
Calculate the mass in grams for each of the following
37. 3.0 moles Na
38.
6.0 moles of O2
39. 2.5 moles Ca
40.
4.0 moles of Al
41. 5.0 moles Mg
42.
3.0 moles H2
43. 0.50 moles Cl2
44.
2.0 moles H2SO4
45. 3.5 moles CaCO3
46.
5.0 moles KI
47. 0.25 moles MgCl2
48.
1.5 moles Ca(OH)2
49. 3.0 moles Al2O3
50.
0.50 moles Ca(NO2)2
Calculate the number of moles of each of the following
51. 200.0 g F2
52.
150.0 g of Zn
53. 25.0 g Li
54.
160.0 g Br2
55. 60.0 g Ne
56.
250.0 g Fe
57. 180.0 g Ca
58.
32.0 g SO2
59. 200.0 g NaOH
60.
10.0 g Na2S
61. 100.0 g MgCO3
62.
60.0 g K2SO4
63. 50.0g ZnO
64.
80.0g H2O2
Calculate the number of atoms, molecules or ions for each of the following
65. 2.0 moles Na atoms
66.
25.0 g S atoms
67. 1.0 mole N atoms
68.
20.0 g Ca atoms
69. 46 g Na atoms
70.
2.0 moles CO2 molecules
71. 3.0 moles K+ ions
72.
35 g H2O molecules
73. 68 g H2S molecules
74.
0.50 moles Mg+2 ions
8-2
HC/CC/TG KHS
Chemical Quantities
Exercise #2
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Mole/ Gram Problems
1. How many grams are in 7.20 moles of dinitrogen trioxide?
2. Find the number of moles in 922 g of iron(III)oxide.
3. Calculate the number of grams in 2.4 moles of potassium oxalate.
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4. Calculate the number of moles in 450 g of barium silicate.
5. How many moles are in 1206 g of calcium sulfate?
6. 0.346 g of chromium (III) bromide contains how many moles?
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7. Calculate the number of moles in 899.99 g of ammonium acetate.
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8. How many grams are in 4.5 mol of hydrogen phosphate?
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9. 0.056 mol of iron(II)permanganate has what mass?
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10. What mass of sodium carbonate would be equal to 1.24 mol?
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11. What is the mass of 0.066 mol of potassium nitrate?
12. What is the formula mass of strontium chloride?
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13. What is the formula mass of sodium carbonate?
14. How many grams of sodium sulfate are in 5.4 moles of sodium sulfate?
15. How many moles are in 560 g of calcium phosphate?
16. How many moles are in 5.6 x 103 g of ammonium oxalate?
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17. How many g of iron (III)perchlorate are in 625 moles?
18. 1250 g of plumbous silicate was used in an experiment. Calculate the
number of moles contained in the amount of this substance.
19. If 4.57 moles of ammonium acetate were used to activate a chemical
reaction, how many grams were needed?
20. Determine which substance provides the most mass; 3.5 moles of
iron(III) carbide or 3.5 moles of iron (III) oxide
21. Calculate the number of moles contained in 5.6 x 105 grams of silver
nitrate
22. Determine the number of moles in 450g of potassium dichromate.
23. Which has more mass, 3.5 moles of calcium carbonate or 3.5 moles of
calcium phosphate?
24. Which has more moles, 100.0g of sodium hydroxide or 100.0 g of
potassium hydroxide?
25. What mass of water would it take to give you one mole?
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8-3
HC/CC/TG KHS
Chemical Quantities
Exercise #4
Chemical Quantities Practice Problems
For the following determine moles or grams
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1. moles in 56g of calcium phosphate
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2. grams in 5.6 moles of silver nitrate
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3. grams in 6.7 moles of zinc acetate
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4. moles in 5678.7g of ferric sulfide
5. moles in 1.2 x 104 g of mercurous nitrate
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6. moles in 457.17 g of potassium oxalate
7. grams in 0.034 moles of copper (II) sulfate
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8. grams in 1.2 x 10-2 moles aluminum silicate
9. grams in 0.006 moles of mercury (I) bicarbonate
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10. moles in 5.6 x 104 g of magnesium chlorate
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For the following calculate the gram formula mass
11. aluminum acetate
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12. calcium nitrate
13. nitrogen trioxide
14. mercuric chloride
15. silicon tetraflouride
16. tin (IV) sulfite
17. ammonium hydroxide
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18. strontium acetate
19. Calcium hydroxide
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20. Hydrogen phosphate
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For the following calculate number of particles
21. 0.50 moles of sodium chloride
22. 15.3 grams of barium chloride
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23. 8.0 moles of silver sulfate
24. 76.0 grams of aluminum bromide
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25. 4.6 moles of calcium flouride
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HC/CC/TG KHS
Chemical Quantities
Exercise #5
Percent Composition
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4.
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5.
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6.
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7.
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8.
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9.
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What is the percent composition of H in H2O?
What is the % composition of Al in AlPO4?
What is the % composition of Ca in Ca(OH)2?
What is the % composition of C in Ba(C2H3O2)2?
What is the % of Pb in PbCl4?
What is the % composition of NH4 in (NH4)2SO3?
What is the % composition of hydrogen in calcium hydroxide?
What is the % composition of oxygen in CO2
A 5.2 g piece of magnesium combines with 3.1g of oxygen to
form a compound, what is the % composition of magnesium in
this compound?
10. A 2.2g piece of sodium combines with 6.3g of iodine to form a
compound. What is the % composition of iodine in this
compound?
11. A 15.2g piece of sulfur combines with 9.4g of potassium to form
a compound. What is the % of potassium in the compound?
12. A 1.5g piece of barium combines with 9.0g of phosphorous to
form a compound. What is the % composition of barium in this
compound?
13. An 8.20g piece of magnesium combines completely with 5.40g of
chlorine to form a compound. What is the % composition of this
compound?
14. Calculate the % composition of carbon in calcium acetate.
15. Calculate the percent of sulfur in sodium bisulfate.
16. Which compound contains the most hydrogen;
a. 20.0g of potassium hydrogen sulfate
b. 124g of calcium acetate
c. 378g of hydrogen cyanide
17. If 500g of sodium chloride were analyzed, how many grams of
sodium metal would be found?
18. How many grams of hydrogen can be derived from 5.6 x 105 g of
water?
19. Iron metal can be extracted from iron ore. There are two types of
iron ore, iron (III) oxide and iron (II) oxide. If you had 800.0g of
each ore, which ore would produce the most iron metal?
20. How many moles in 30.0 cm3 of copper? (the density of copper is
8.92g/cm3)
8-5
HC/CC/TG KHS
Chemical Quantities
Empirical Formula
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1. What is the empirical formula of a compound containing 63g of Rb and
5.9g of O?
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2. What is the empirical formula of a compound with 0.159g of U and
0.119g of Cl?
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3. Write the empirical formula for the compound that has 7.22g of Ni,
2.53g of P, and 5.25g of O.
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4. If a compound contains 0.285g of Ca, 0.236g of S and 0.469g of O,
what is its empirical formula?
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5. If a compound is made up of 32.8% Cr and 67.2% Cl, what is it’s
empirical formula?
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6. What is the empirical formula of a compound found to contain 42.7%
Co and 57.3% Se?
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7. Find the empirical formula of a compound that is 56.6% La and 43.4%
Cl.
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8. What is the empirical formula of a compound that is 81.95 Ta and
18.1% O?
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9. If the % composition of a compound is 92.3% C and 7.7% H, what is
the empirical formula?
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10. Find the empirical formula of a compound with a % composition of
26.7% P, 12.2% N and 61.2% Cl.
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11. A hydrate was analyzed to determine that it contained 5.262g of
Tl(NO3)3 and 0.789g of water, what is the formula of the hydrate?
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12. What is the formula for a hydrate if it contains 2.94g of Sn(NO3)2 and
4.37g of water?
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13. In a chemical reaction, 1.58g of copper combine with sulfur to give
1.98g of a new compound. What is the empirical formula of this new
compound?
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14. An analysis determines that a compound is made of 42.9% carbon and
57.1% oxygen, what is the empirical formula?
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15. In a chemical process the following data was collected. 44.5% copper
and 55.7% bromine. Calculate the correct empirical formula for the
compound.
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16. From the following data determine the correct empirical formula.
38.9% Ba, 29.4% Cr and 31.7% O.
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17. In a chemical reaction, 0.274g of aluminum combine with iodine to
form 4.41g of a new product. What is the empirical formula of this
product?
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18. What is the empirical formula of a compound containing 9.93%
carbon, 58.6% chlorine and 31.1% fluorine?
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HC/CC/TG KHS
Chemical Quantities
Molecular Formula
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1. The molecular formula of a compound is either the same as its empirical
formula or a _______ of it.
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2. What do you need to know to calculate the molecular formula of a
compound?
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3. If you divide the molecular mass of a compound by the empirical formula
mass, what is the result?
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4. What would you use to convert the empirical formula of a compound to a
molecular formula?
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5. Gas X is found to be 24.0% carbon and 76.0% fluorine, what is its
empirical formula?
Given that the molar mass of gas X is 200.04 g/mol, determine its
molecular formula.
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6. Ribose is an important sugar (part of RNA), with a molar mass of 150.15
g/mol. If its empirical formula is CH2O, what is its molecular formula?
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7. Naphthalene is a soft covalent solid that is often used in mothballs. Its
molar mass is 128.18 g/mol and it contains 93.75% carbon and 6.25%
hydrogen. Determine the molecular formula of naphthalene from this
data.
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8. What is the molecular formula for a compound with a molecular mass of
30.0 g/mol containing 80.0% hydrogen and 20.0 % oxygen?
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9. If a compound contains 37.8% carbon 6.3% hydrogen, 55.8% chlorine
and a molecular mass of 127.0g/mol, what is the molecular formula
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HC/CC/TG KHS
Chemical Quantities
Chemical Quantities Review
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1. What is the molecular mass of dinitrogen pentoxide?
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2.
3.
4.
5.
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6.
7.
8.
9.
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Calculate the formula weight of aluminum silicate.
What is the % composition of phosphorous in plumbic phosphate?
What is the % composition of each element in barium acetate?
What is the mass of 3.04 moles of sodium carbonate?
How many atoms are there in 84.4g of carbon
How many moles are in 481g of magnesium phosphate?
What is the mass of 5.94 x 1024 formula units of calcium chlorate?
A 5.2g piece of magnesium combines with 3.1g of oxygen, what is the %
composition of magnesium in the compound?
10. If 15.2g of sulfur combine with 9.4g of potassium, what is the % composition of
potassium in the compound?
11. What is the % composition of a compound formed when 6.3g of iodine combine w
2.2g of sodium?
12. What is the empirical formula for a compound that contains 23.6g of sulfur, 46.9g
oxygen and 29.5g of calcium?
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13. Find the empirical formula for the compound with the following analysis: 8.54g M
16.78g C, 2.1g H, 22.49g O.
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14. Find the empirical formula for the compound with the following analysis: 9.93%
carbon, 58.6% chlorine, and 31.3% fluorine.
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15. What is the empirical formula for a compound that contains 5.03g of aluminum
and 8.97g of sulfur?
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16. What is the percent composition of magnesium in 3.50 mole of magnesium
nitride?
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17. A compound is found to contain 33.3% calcium, 40.0% oxygen, and 26.7%
sulfur. What is the empirical formula for the compound?
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18. What is the molecular formula of a compound with a molecular mass of 78
g/mol if the % composition is 92.3% carbon, and 7.7% hydrogen?
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19. A compound is found to have a percent composition of 80.4% bismuth, 18.5%
oxygen and 1.16% hydrogen. What is the empirical formula?
8-8
HC/CC/TG KHS
Chemical Quantities
Lab #3
Chapter 8 LAB: DETERMINATION OF THE FORMULA OF A HYDRATE
OBJECTIVE: Given a sample of hydrated salt and appropriate apparatus, the student
will be able to experimentally determine the correct formula for the compound.
APPARATUS: goggles, Bunsen burner, matches, crucible, triangle, crucible tongs,
ringstand and ring, spatula, balance.
PROCEDURE:
1. Weigh a crucible to the nearest 0.01 gram. Add approximately 2 grams of salt.
Record total weight of salt and crucible to the nearest 0.01 gram. Subtract to find
the weight of your salt.
2. Support the crucible on the triangle at an appropriate height to receive the
maximum heat of the flame. WARNING: hydrates, upon heating, can decrepitate
(explode). Protect your eyes at all times. Heat the crucible gently at first. Too
rapid heating may cause loss by spattering because the water of hydration is
driven off too rapidly. Gradually heat more strongly, keeping the crucible in the
hottest part of the flame. After ten minutes of strong heating, gradually withdraw
the flame, wait a moment, then use the crucible tongs to move the crucible to the
base of the ringstand to cool for at least three minutes. Never put a hot crucible
on a balance. When cooled enough to touch, move to the balance with crucible
tongs, weigh and record.
3. Repeat the heating, cool, and reweigh. Continue this process until you get two
successive weighing within 0.20 grams. This is called “heating to constant
weight”. Discard the used, now anhydrous salt in the trash. The crucible may
then be washed out with tap water.
4. SHOW ALL CALCULATIONS CLEARLY AND NEATLY. WATCH
SIGNIFICANT DIGITS.
a. Use the lowest weight to find the mass of anhydrous salt.
b. Find the formula mass of your salt.
c. Find moles of your salt.
d. Subtract the two masses to find the mass of water
e. Find moles of water
f. Right the formula for the hydrate
g. Calculate the percentage of water in the hydrated salt
h. Find the formula mass of the hydrated salt.
i. Calculate the “theoretical percentage of water in the hydrate
j. Calculate your percent error.
8-9
HC/CC/TG KHS