Name: 
 

Unit 6 Practice Test - No Molarity


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

 1. 
Avogadro’s number refers to the number of particles in one gram of a substance.
 

 2. 
One mole of a substance has the same volume as one mole of any other substance, regardless of what substances are being compared.
 

 3. 
One mole of a substance has the same number of particles as one mole of any other substance, regardless of what substances are being compared.
 

 4. 
To find the percent by mass of a compound if you are given the formula, divide the molar mass of that element in one mole of the compound by the total molar mass of the compound.
 

 5. 
The empirical formula for a compound consists of the symbols for the elements in the compound without any subscripts.
 

 6. 
The percent by mass of each element in a compound is known as the percent composition of a compound.
 

 

 7. 
The formula for carbon dioxide, CO2, can represent
a.
one molecule of carbon dioxide.
b.
1 mol of carbon dioxide molecules.
c.
the combination of 1 atom of carbon and 2 atoms of oxygen.
d.
all of the above.
 

 8. 
What is the formula mass of ethyl alcohol, C2H5OH?
a.
30.33 amu
b.
33.27 amu
c.
45.06 amu
d.
46.08 amu
 

 9. 
The molar mass of NO2 is 46.01 g/mol. How many moles of NO2 are present in 114.95 g?
a.
0.4003 mol
b.
1.000 mol
c.
2.498 mol
d.
114.95 mol
 

 10. 
The molar mass of CCl4 is 153.81 g/mol. How many grams of CCl4 are needed to have 5.000 mol?
a.
5 g
b.
30.76 g
c.
769.0 g
d.
796.05 g
 

 11. 
The molar mass of H2O is 18.02 g/mol. How many grams of H2O are present in 0.20 mol?
a.
0.2 g
b.
3.6 g
c.
35.9 g
d.
89.9 g
 

 12. 
The molar mass of NH3 is 17.03 g/mol. How many moles of NH3 are present in 107.1 g?
a.
0.1623 mol
b.
3.614 mol
c.
6.289 mol
d.
107.1 mol
 

 13. 
How many oxygen atoms are there in 0.500 mol of CO2?
a.
6.02 mc013-2.jpg 1023
b.
3.01 mc013-3.jpg 1023
c.
15.9994
d.
11.0
 

 14. 
How many molecules are there in 5.0 g of methyl alcohol, CH3OH?
a.
9.4 mc014-2.jpg 1022
b.
3.0 mc014-3.jpg 1024
c.
3.6 mc014-4.jpg 1024
d.
3.8 mc014-5.jpg 1024
 

 15. 
What is the percentage composition of CF4?
a.
20% C, 80% F
c.
16.8% C, 83.2% F
b.
13.6% C, 86.4% F
d.
81% C, 19% F
 

 16. 
What is the percentage composition of CO?
a.
50% C, 50% O
c.
25% C, 75% O
b.
12% C, 88% O
d.
43% C, 57% O
 

 17. 
The percentage composition of sulfur in SO2 is about 50%. What is the percentage of oxygen in this compound?
a.
25%
b.
50%
c.
75%
d.
90%
 

 18. 
A formula that shows the simplest whole-number ratio of the atoms in a compound is the
a.
molecular formula.
c.
experimental formula.
b.
ideal formula.
d.
empirical formula.
 

 19. 
What is the empirical formula for a compound that is 31.9% potassium, 28.9% chlorine, and 39.2% oxygen?
a.
KClO2
b.
KClO3
c.
K2Cl2O3
d.
K2Cl2O5
 

 20. 
What is the empirical formula for a compound that is 43.6% phosphorus and 56.4% oxygen?
a.
P3O7
b.
PO3
c.
P2O3
d.
P2O5
 

 21. 
A compound contains 259.2 g of F and 40.8 g of C. What is the empirical formula for this compound?
a.
CF4
b.
C4F
c.
CF
d.
CF2
 

 22. 
A compound contains 64 g of O and 8 g of H. What is the empirical formula for this compound?
a.
H2O
b.
H2O2
c.
HO2
d.
HO
 

 23. 
A molecular compound has the empirical formula XY3. Which of the following is a possible molecular formula?
a.
X2Y3
b.
XY4
c.
X2Y5
d.
X2Y6
 

 24. 
A compound's empirical formula is C2H5. If the formula mass is 58 amu, what is the molecular formula?
a.
C3H6
b.
C4H10
c.
C5H8
d.
C5H15
 

 25. 
A compound's empirical formula is N2O5. If the formula mass is 108 amu, what is the molecular formula?
a.
N2O5
b.
N4O10
c.
NO3
d.
N2O4
 

 26. 
A compound's empirical formula is CH. If the formula mass is 26 amu, what is the molecular formula?
a.
C2H2
b.
CH3
c.
CH4
d.
C4H
 

 27. 
What is the mass percentage of chlorine in NaCl?
a.
35.45%
c.
60.7%
b.
50%
d.
64.5%
 

 28. 
To find the molecular formula from the empirical formula, one must determine the compound's
a.
density.
c.
structural formula.
b.
formula mass.
d.
crystal lattice.
 

 29. 
A compound's empirical formula is CH3. If the formula mass is 30 amu, what is the molecular formula?
a.
CH3
c.
C2H6
b.
CH4
d.
C3H9
 

 30. 
How many grams of phosphorus are in 500.0 grams of calcium phosphorus?
a.
49.92 grams
c.
310.2 grams
b.
99.84 grams
d.
130.1 grams
 

 31. 
Calculate the number of molecules in 4.0 mol H2O.
a.
0.60 ´ 1023 molecules
c.
2.4 ´ 10–23 molecules
b.
2.4 ´ 1024 molecules
d.
2.4 ´ 1023 molecules
 

 32. 
Which of the following elements exists as a diatomic molecule?
a.
neon
c.
nitrogen
b.
lithium
d.
sulfur
 

 33. 
All of the following are equal to Avogadro's number EXCEPT ____.
a.
the number of atoms of bromine in 1 mol Brmc033-1.jpg
b.
the number of atoms of gold in 1 mol Au
c.
the number of molecules of nitrogen in 1 mol Nmc033-2.jpg
d.
the number of molecules of carbon monoxide in 1 mol CO
 

 34. 
Which of the following compounds has the highest oxygen content, by weight?
a.
Namc034-1.jpgO
c.
BaO
b.
COmc034-2.jpg
d.
Hmc034-3.jpgO
 

 35. 
What is true about the molar mass of chlorine gas?
a.
The molar mass is 35.5 g.
b.
The molar mass is 71.0 g.
c.
The molar mass is equal to the mass of one mole of chlorine atoms.
d.
none of the above
 

 36. 
What is the number of moles of beryllium atoms in 36 g of Be?
a.
0.25 mol
c.
45.0 mol
b.
4.0 mol
d.
320 mol
 

 37. 
The volume of one mole of a substance is 22.4 L at STP for all ____.
a.
gases
c.
solids
b.
liquids
d.
compounds
 

 38. 
What is the number of moles in 500 L of He gas at STP?
a.
0.05 mol
c.
22 mol
b.
0.2 mol
d.
90 mol
 

 39. 
Given 1.00 mole of each of the following gases at STP, which gas would have the greatest volume?
a.
He
c.
SOmc039-2.jpg
b.
Omc039-1.jpg
d.
All would have the same volume.
 

 40. 
The lowest whole-number ratio of the elements in a compound is called the ____.
a.
empirical formula
c.
binary formula
b.
molecular formula
d.
representative formula
 

 41. 
What is the percent composition of carbon, in heptane, Cmc041-1.jpgHmc041-2.jpg?
a.
12%
c.
68%
b.
19%
d.
84%
 

 42. 
Which of the following is NOT an empirical formula?
a.
Cmc042-1.jpgNmc042-2.jpgHmc042-3.jpg
c.
BeCrmc042-6.jpgOmc042-7.jpg
b.
Cmc042-4.jpgHmc042-5.jpgO
d.
Sbmc042-8.jpgSmc042-9.jpg
 

 43. 
What is the empirical formula of a compound that is 40% sulfur and 60% oxygen by weight?
a.
SO
c.
SOmc043-2.jpg
b.
SOmc043-1.jpg
d.
Smc043-3.jpgOmc043-4.jpg
 

 44. 
How many moles of tungsten atoms are in 4.8 mc044-1.jpg 10mc044-2.jpg atoms of tungsten?
a.
8.0 mc044-3.jpg 10mc044-4.jpg moles
c.
1.3 mc044-7.jpg 10mc044-8.jpg moles
b.
8.0 mc044-5.jpg 10mc044-6.jpg moles
d.
1.3 mc044-9.jpg 10mc044-10.jpg moles
 

 45. 
Which of the following is NOT true about empirical and molecular formulas?
a.
The molecular formula of a compound can be the same as its empirical formula.
b.
The molecular formula of a compound can be some whole-number multiple of its empirical formula.
c.
Several compounds can have the same empirical formula, but have different molecular formulas.
d.
The empirical formula of a compound can be triple its molecular formula.
 



 
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