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Online Study Guide Chem 1 - Moles



True/False
Indicate whether the sentence or statement is true or false.
 

 1. 

In one mole of freon, the chemical ratio of carbon to chlorine to fluorine is 2:1:2.
 

 2. 

The percent by mass of each element in a compound is known as the percent composition of a compound.
 

 3. 

The molecular formula for a compound is the formula with the smallest whole-number mole ratio of the elements.
 

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 4. 

A mole of potassium chloride (KCl) contains mole_files/i0060000.jpg _____.
a.
atoms KCl.
c.
ions KCl.
b.
formula units KCl.
d.
molecules KCl.
 

 5. 

The SI unit of molar mass is the _____.
a.
gram.
c.
mole.
b.
gram/mole.
d.
mole/gram.
 

 6. 

Which conversion factor would you use to calculate correctly the mass of 2 moles of the element titanium?
a.
mole_files/i0080000.jpg
c.
mole_files/i0080001.jpg
b.
mole_files/i0080002.jpg
d.
mole_files/i0080003.jpg
 

 7. 

How many moles of oxygen atoms do 1.5 moles of CO2 contain?
a.
1 mol
c.
2 mol
b.
1.5 mol
d.
3.0 mol
 

 8. 

Which compound has the smallest molar mass?
a.
CO
c.
H2O
b.
CO2
d.
H2O2
 

 9. 

One mole of silicon (Si) has a mass of 28.086 g, and one mole of carbon has a mass of 12.011 g. What is the mass of one mole of silicon carbide (SiC)?
a.
2.340 g
b.
16.075 g
c.
40.097 g
d.
3.3734 ´ 102 g
 

 10. 

Methane (CH4) contains 75% carbon. What percentage of methane is hydrogen?
a.
4%
c.
25%
b.
6%
d.
33%
 

 11. 

Which information about a compound can you use to begin to determine the empirical and molecular formulas of the compound?
a.
mass of the compound
c.
percent composition of the compound
b.
number of elements in the compound
d.
volume of the compound
 

 12. 

You have determined that a compound is composed of 0.300 moles of carbon and 0.600 moles of oxygen. What must you do to determine the mole ratio of the elements in the empirical formula of the compound?
a.
Multiply each mole value by 0.300 mol.
c.
Divide each mole value by 0.300 mol.
b.
Multiply each mole value by 0.600 mol.
d.
Divide each mole value by 0.600 mol.
 

 13. 

The mole ratio of carbon to hydrogen to oxygen in a compound is 1 mol C : 2 mol H : 1 mol O. What is the empirical formula of the compound?
a.
CHO
c.
C2HO2
b.
CH2O
d.
C2H2O2
 

 14. 

You calculate the mole ratio of oxygen to aluminum in a compound to be 1.5 mol O : 1 mol Al. What should you do to determine the mole ratio in the empirical formula of the compound?
a.
Multiply each mole value by 1.5.
c.
Divide each mole value by 1.5.
b.
Multiply each mole value by 2.
d.
Divide each mole value by 2.
 

 15. 

What is the relationship between the molecular formula and the empirical formula of a compound?
a.
(molecular formula)(empirical formula) = n
b.
molecular formula = mole_files/i0170000.jpg
c.
molecular formula = (empirical formula)n
d.
molecular formula =mole_files/i0170001.jpg
 

 16. 

You know that the empirical formula of a compound has a molar mass of 30.0 g/mol. The experimental molar mass of this compound is 60.0 g/mol. What must you do to determine the value of n in the relationship between the molecular formula and the empirical formula?
a.
Add 30.0 g/mol and 60.0 g/mol.
c.
Divide 60.0 g/mol by 30.0 g/mol.
b.
Divide 30.0 g/mol by 60.0 g/mol.
d.
Multiply 30.0 g/mol by 60.0 g/mol.
 

 17. 

You know that the experimental molar mass of a compound is three times the molar mass of its empirical formula. If the compound’s empirical formula is NO2, what is its molecular formula?
a.
NO2
c.
N3O2
b.
NO6
d.
N3O6
 

 18. 

What is the SI base unit used to measure the amount of a substance?
a.
Kelvin
c.
Meter
b.
Kilogram
d.
Mole
 

 19. 

Calculate the number of molecules in 4.0 mol H2O.
a.
0.60 x 1023 molecules
c.
2.4 x 10–23 molecules
b.
2.4 x 1024 molecules
d.
2.4 x 1023 molecules
 

 20. 

How many moles of Ag contain 4.49 ´ 1023 atoms Ag?
a.
0.745 x 1024 mol
c.
0.745 mol
b.
0.745 x 1023 mol
d.
27.0 mol
 

 21. 

Calculate the number of atoms in 13.2 mol copper.
a.
2.19 x 1023 atoms
c.
7.95 x 10–23 atoms
b.
7.95 x 1024 atoms
d.
79.5 x 1023 atoms
 

 22. 

Copper (Cu) is a transition element used in the making of coins. Calculate the mass in grams of 0.0420 moles of copper.
a.
0.00697 g
c.
2.67 g
b.
0.252 g
d.
6.61 g
 

 23. 

Determine the mass in grams of 0.0489 mol cobalt.
a.
0.00812 g
c.
2.88 g
b.
0.294 g
d.
0.000830 g
 

 24. 

How many moles of calcium are in 425 g calcium (Ca)?
a.
10.6 mol
c.
171 mol
b.
70.5 mol
d.
255 mol
 

 25. 

Copper is one of a group of metals called the coinage metals. How many atoms of copper (Cu) are in a pure copper coin weighing 12.0 g?
a.
0.0313 x 1023 atoms
c.
1.10 x 1023 atoms
b.
0.187 x 1023 atoms
d.
1.13 x 1023 atoms
 

 26. 

A balloon contains 4.50 ´ 1022 atoms of helium (He) gas. Calculate the mass of helium in grams.
a.
0.185 g
c.
0.0747 g
b.
0.0185 g
d.
0.299 g
 

 27. 

What is the molar mass of Ca(OH)2?
a.
57.008 g/mol
c.
73.088 g/mol
b.
73.080 g/mol
d.
74.092 g/mol
 

 28. 

What is the mass of 2.25 moles of sulfuric acid (H2SO4)?
a.
50.0 g
c.
112 g
b.
98.0 g
d.
220 g
 

 29. 

How many grams of potassium permanganate are in 2.20 moles?
a.
53.2 g
c.
242 g
b.
158 g
d.
347 g
 

 30. 

Determine the number of moles present in 32.5 g aluminum chloride.
a.
0.244 mol
c.
1.21 mol
b.
4.10 mol
d.
720 mol
 

 31. 

What is the mass in grams of 1.02 x 1024 atoms manganese (Mn)?
a.
0.112 x 101 g
c.
9.30 x 10–1 g
b.
0.169 x 101 g
d.
9.30 x 101 g
 

 32. 

How many moles are present in 21.2 g hydrochloric acid?
a.
0.582 mol
c.
21.0 mol
b.
1.72 mol
d.
128 mol
 

 33. 

The molecular mass of potassium dichromate, K2Cr2O7, is __________.
a.
107.09
d.
294.18
b.
255.08
e.
333.08
c.
242.18
 

 34. 

The molecular mass of the ionic compound (NH4)2SO4 is __________.
a.
100
d.
132
b.
118
e.
264
c.
116
 

 35. 

What is the mass % of carbon in dimethylsulfoxide, C2H6SO?
a.
60.0
d.
7.74
b.
20.6
e.
79.8
c.
30.7
 

 36. 

The mass % of F in the binary compound KrF2 is __________.
a.
18.48
d.
81.52
b.
145.3
e.
31.20
c.
68.80
 

 37. 

A compound was found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen.  What is the empirical formula of the compound?
a.
CH2O
d.
C3H6O
b.
C6HO8
e.
C4H7O53
c.
C2H4O2
 

 38. 

A compound containing only carbon and hydrogen is 85.7% by mass carbon and 14.3% by mass hydrogen.  What is the empirical formula of the compound?
a.
CH2
d.
C4H8
b.
C2H4
e.
C86H14
c.
CH4
 

Matching
 
 
Match the terms below with their correct definitions.
a.
Avogadro’s number
e.
mole
b.
empirical formula
f.
molecular formula
c.
hydrate
g.
percent composition
d.
molar mass
 

 39. 

Percent by mass of each element in a compound
 

 40. 

Mass in grams of one mole of any pure substance
 

 41. 

Formula of a compound with the smallest whole-number mole ratio of the elements
 

 42. 

Specifies the actual number of atoms of each element in one molecule of a compound
 

 43. 

SI base unit used to measure the amount of a substance
 

 44. 

mole_files/i0480000.jpg
 
 
Match the letter of the conversion factor that is needed to solve the problem. You may need to use more than one conversion factor to solve the problem.
a.
mole_files/i0490000.jpg
c.
mole_files/i0490001.jpg
b.
mole_files/i0490002.jpg
d.
mole_files/i0490003.jpg
 

 45. 

Find the number of moles in 23.0 g of zinc.
 

 46. 

Find the mass of 5.0 ´ 1020 zinc atoms.
 

 47. 

Find the mass of 2.00 moles of zinc.
 

 48. 

Find the number of atoms in 7.40 g of zinc.
 

 49. 

Find the number of moles that contain 4.25 ´ 1027 zinc atoms.
 

 50. 

Find the number of atoms in 3.25 moles of zinc.
 



 
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