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Moles Review
1) Given two formulas representing the same
compound:
Formula A CH3
Formula B C2H6
Which statement describes these formulas?
1) Formulas A and B are both empirical.
2) Formulas A and B are both molecular.
3) Formula A is empirical, and formula B is
molecular.
4) Formula A is molecular, and formula B is
empirical.
2) What is the empirical formula of a compound
that has a carbon-to-hydrogen ratio of 2 to 6?
1) CH3
2) C2H6 3) C3H
4) C6H2
3) What is the total number of atoms represented
in the formula CuSO4 • 5H2O?
1) 8
2) 13
3) 21
4) 27
4) What is the empirical formula of a compound
that contains 0.20 mole of nitrogen atoms and
0.40 mole of oxygen atoms?
1) NO2
2) N2O 3) N2O4 4) N4O2
5) A compound has the empirical formula CH2O and
a gram-formula mass of 60. grams per mole.
What is the molecular formula of this
compound?
1) CH2O
2) C2H4O2
3) C3H8O
4) C4H8O4
6) Which formula is both a molecular and an
empirical formula?
1) C6H12O6
2) C2H4O2
3) C3H8O
4) C4H8
7) What is the gram-formula mass of (NH4)3PO4?
1) 112 g/mol
2) 121 g/mol
3) 149 g/mol
4) 242 g/mol
8) What is the formula mass of Al2(SO4)3?
1) 123
2) 150
3) 214
4) 342
9) What is the gram formula mass of Na2CO3 •
10H2O?
1) 106 g
2) 142 g
3) 266 g
4) 286 g
10) What is the total number of moles of hydrogen
in 1 mole of (NH4)2HPO4?
1) 5
2) 7
3) 8
4) 9
11) The total number of moles represented by 20
grams of CaCO3 is
1) 1
2) 2
3) 0.1
4) 0.2
12) Which quantity is equivalent to 39 grams of
LiF?
1) 1.0 mole
2) 2.0 moles
3) 0.50 mole
4) 1.5 moles
13) A substance has an empirical formula of CH2
and a molar mass of 56 grams per mole. The
molecular formula for this compound is
1) CH2
2) C4H6 3) C4H8 4) C8H4
14) A compound contains 46.7% nitrogen and
53.3% oxygen by mass. What is the empirical
formula of the compound?
1) NO
2) N2O
3) N2O3
4) N2O5
15) What is the empirical formula of a compound
consisting of 29.6% oxygen and 70.4% fluorine
by mass?
1) OF
2) OF2 3) O2F
4) O2F4
16) What is the empirical formula of a compound if
a sample contains 8.52 grams of carbon and
1.42 grams of hydrogen?
1) C2H
2) CH2
3) CH
4) C2H2
17) What is the percent composition by mass of
hydrogen in NH4HCO3 (gram-formula mass =
79 grams/mole)?
1) 5.1% 2) 6.3% 3) 10.% 4) 50.%
18) A hydrate is a compound that includes water
molecules within its crystal structure. During
an experiment to determine the percent by
mass of water in a hydrated crystal, a student
found the mass of the hydrated crystal to be
4.10 grams. After heating to constant mass,
the mass was 3.70 grams. What is the percent
by mass of water in this crystal?
1) 90.%
2) 11%
3) 9.8%
4) 0.40%
19) A 20. gram sample of a hydrate is heated until
all the water of hydration is driven off. The
mass of the anhydrous compound remaining is
15 grams. What is the percent by mass of
water in the hydrate?
1) 75% 2) 33% 3) 25% 4) 15%
20) What is the total number of nitrogen atoms in
0.25 mole of NO2 gas?
1) 1.5 × 1023
2) 6.0 × 1023
3) 3.0 × 1023
4) 1.2 × 1024
21) How many molecules are contained in 127
grams of iodine (I2)?
1) 1.50 × 1023
2) 3.01 × 1023
3) 9.03 × 1023
4) 12.4 × 1023
22) What is the total number of atoms contained
in 80. grams of neon?
1) 6.0 × 1023
2) 1.2 × 1024
3) 2.4 × 1024
4) 4.8 × 1024
23) At STP, which sample contains the same
number of molecules as 11.2 liters of CO2(g) at
STP?
1) 5.6L of NO2(g)
2) 7.5 L of H2(g)
3) 11.2 L of N2(g)
4) 22.4 L of CO(g)
24) What is the volume, in liters, of 576 grams of
SO2 gas at STP?
1) 101
2) 202
3) 216
4) 788
25) The volume occupied by 9.03 × 1023 molecules
of N2 gas at STP is closest to
1) 0.500 liter
2) 1.50 liters
3) 22.4 liters
4) 33.6 liters
26) What is the total volume, in liters, occupied by
56.0 grams of nitrogen gas at STP?
1) 11.2
2) 22.4 3) 33.6 4) 44.8
27) Which quantity of N2 gas has a volume of 11.2
liters at STP?
1) 1.0 mole
2) 2.0 moles
3) 14.0 grams
4) 28.0 grams
28) Write the empirical formula for the compound C6H12O6.
29) Show a correct numerical setup for calculating the formula mass of glucose, C 6H12O6.
30) Base your answer to the following question on
the information below.
A scientist in a chemistry laboratory
determined the molecular formulas for two
compounds containing nitrogen and oxygen
to be NO2 and N2O5
Write an IUPAC name for the compound N 2O5.
31) Show a correct numerical setup for calculating
the number of moles of CO2 (gram-formula
mass = 44 g/mol) present in 11 grams of CO2.
32) Given the compound C4H10O8,
a Calculate the molar mass of the compound.
b Calculate the number of moles in 17.7 grams of the compound.
c What is the empirical formula for this compound?
33) In a laboratory experiment, a student determined the mass of the product, CaCl 2(s), to be 45.5
grams.
a Calculate the gram formula mass of CaCl2(s). Round atomic masses from the Periodic Table
to the nearest tenth. [ Show all work. Indicate the correct answer in proper significant figures
and include an appropriate unit.]
b Calculate the number of moles of CaCl2(s) produced. [Show all work. Indicate the correct
answer in proper significant figures.]