Download Review for Unit 8 Test (answer key)

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Unit 5A Test Review-Answer Key
1. What is the percent composition of Si2O6?
 Si = (2 x 28.09) = 56.18 ÷ 152. 18 x 100 = 36.9 %
 O = (6 x 16)
= 96 ÷ 152. 18 x 100 = 63.1%
Total MM = 152.18
2. What is the percent composition of Ti(SO4)2?
Ti = (1 x 47.88) = 47.88 ÷ 240.02 x 100 = 19.9 %
S = (2 x 32.07) = 64.14 ÷ 240.02 x 100 = 26.7 %
O = (8 x 16)
= 128 ÷ 240.02 x 100 = 53.3%
Total MM = 240.02
3. What is the percent composition of Hydrogen in C6H12O6?
C = (6 x 12.01) = 72.06 ÷ 180.18 x 100
H = (12 x 1.01) = 12.12 ÷ 180.18 x 100 = 6.7 %
O = (6 x 16)
= 96 ÷ 180.18 x 100
Total MM = 180.18
4.
An unknown compound is 43.4% sodium, 11.3% carbon, and 45.3% oxygen. What is the
empirical formula?
Na = 43.4 g x __1 mole__ = 1.89 moles ÷ 0.94 = 2
22.99 g
C = 11.3 g x __1 mole__ = 0.94 moles ÷ 0.94 = 1
12.01 g
Empirical Formula = Na2CO3
O = 45.3 g x __1 mole__ = 2.93 moles ÷ 0.94 = 3
16 g
5. Monosodium glutamate (MSG) is sometimes added to food to enhance flavor. Analysis
determined this compound to be 35.5% C, 4.77% H, 8.28% N, 13.6% Na, and 37.9% O. What
is the empirical formula for MSG?
C = 35.5g x __1 mole__ = 2.96 moles ÷ 0.59 = 5.01 = 5
12.01 g
H = 4.77 g x __1 mole__ = 4.7 moles ÷ 0.59 = 7.96 = 8
1.01 g
N = 8.28 g x __1 mole__ = 0.59 moles ÷ 0.59 = 1
14.01 g
Na = 13.6 g x __1 mole__ = 0.59 moles ÷ 0.59 = 1
22.99 g
O = 37.9 g x __1 mole__ = 2.37 moles ÷ 0.59 = 4.01 = 4
16 g
Empirical Formula = C5H8NNaO4
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6. Vanadium oxide is used as an industrial catalyst. The percent composition of this oxide is
56.0% vanadium and 44.0% oxygen. Determine the empirical formula for vanadium oxide.
V = 56 g x __1 mole__ = 1.1 moles ÷ 1.1 = 1 x 2 = 2
50.94 g
O = 44 g x __1 mole__ = 2.75 moles ÷ 1.1 = 2.5 x 2 = 5
16 g
Empirical Formula = V2O5
7. Define empirical formula. The lowest whole number ratio of elements in a compound.
8.
Which of the following is an empirical formula?
a. C2H4
b. N2O
c. P2O6
d. C3H6O3
9. If the molecular formula is C11H22O11, what is the empirical formula? CH2O
10. All of the following are empirical formulas EXCEPT ―
a. CH4
b. N2O5
c. NH3
d. P4O10
e. H2O
11. Which one of the following is an empirical formula?
a. C2F6
b. N2H4
c. H2SO4
d. P4O10
12. Which of the following is an empirical formula?
a. C4H8O2
b. C2H4O2
c. C2H6O
d. C6H12O6
13. Fill-in-the-blank: Molar mass of an element = 1 mole.
14. List the representative particle for the following:
a. Molecular (covalent) compounds = molecules
b. Ionic Compounds = formula units
c. Elements = atoms
15. What is Avogadro’s number (IN SCIENTIFIC NOTATION)? 6.02 x 1023
16.
Define mole. The SI unit that measures the amount of a substance.
17. Write all the conversion factors for 1 mole.
1 moles = 6.02 x 1023 atoms, molecules, formula units
1 mole = molar mass (g)
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18.
How many atoms of are there in 1.25 moles Sulfur?
1.25 mol x (6.02 x 1023 atoms) = 7.53 x 1023 atoms
1 mol
19. How many moles are in 87.2 grams of SO2?
SO2 molar mass = ( 1 x 32.07) + (2 x 16) = 64.07
87.2 x 1 mol = 1.36 mol
64.07g
20. If you have 3.29 x 1024 atoms of Sodium, how many liters of sodium do you have?
3.29 x 1024 atoms x
22.4 L
= 122.4 L
6.02 x 1023 atoms
21. If you have 2.83 x 1022 molecules of CO2, how many moles of CO2 do you have?
2.83 x 1022 molecules x
1 mole
= 0.47 moles
6.02 x 1023 molecules
22. If you have 2.12 moles of NO, how many liters of NO do you have?
2.12 moles x
22.4 L
= 47.49 L
1 mole
23. If you have 1 mole of Au, how many atoms of gold do you have? (Hint: Do not calculate this
question!) 1 mol = 6.02 x 1023 atoms
24. Find the molar mass of Al2(SO4)3.
(26.98 x 2) + (32.07 x 3) + (16 x 12) = 342.17 g
25. If you were to calculate the molar mass of BeF2, how many moles of each element are in this
compound? 1 mole of Be and 2 moles of F
26. What is the molar mass of CO2?
(1 x 14.01) + (2 x 16) = 44.01 g
27. What is the molar mass of Pb3(PO4)4?
(3 x 207.2) + (4 x 30.97) + (16 x 16) = 1001.48 g
28. If you have 2.2 moles of NaCl, how many grams of NaCl do you have?
2.2 moles x
58.44 g
= 128.57 g
1 mole
NaCl molar mass = ( 1 x 22.99) + (1 x 35.45) = 58.44
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29. If you have 32.9 grams of H2O, how many liters of H2O do you have?
32.9 grams x
22.4 L
= 40.9 L
18.02 g
H2O molar mass = ( 2 x 1.01) + (1 x 16) = 18.02
30. If you have 0.385 liters of CaSO4, how many grams of CaSO4 do you have?
0.385 liters x
136.15 g
= 2.34 grams
22.4 L
CaSO4 molar mass = ( 1 x 40.08) + (1 x 32.07) + (4 x 16) = 136.15
31. How many grams would 3.84 x 1023 atoms of Silicon weigh?
3.84 x 1023 atoms x
28.09 g
= 17.92 g
23
6.02 x 10 atoms
Si molar mass = 28.09
32. How many atoms are in 39.2 grams of Calcium?
39.2 grams x
6.02 x 1023 atoms
40.08 g
= 5.89 x 1023 atoms
Ca molar mass = 40.08
33. What is the molar mass of Ca(NO3)2?
(1 x 40.08) + (2 x 14.01) + (6 x 16) = 164.1 g
34. What is the molar mass of (NH4)3PO4?
(3 x 14.01) + (12 x 1.01) + (1 x 30.97) + (4 x 16) = 149.12 g