CHEM 107
Problem Set #1
S. S. Massoud
Answer the following questions:
Part I: Multiple Choices. Circle the ONE best answer:
1. Which of the following is a homogeneous mixture?
a) muddy water
b) milk
d) melted rocky road ice cream
c) Italian salad dressing
e) White wine
2. Which of the following does not represent a chemical change?
a) iron rusting
d) leaves changing color
b) boiling egg
c) digestion of food
e) dissolving sugar in water
3. How many μg are in 0.0134 g?
a) 1.34 x 10-4
d) 1.34 x 104
b) 1.34 x10-6
e) 1.34 x 106
c) 1.34
4. Convert 184˚ F to degree Celsius.
a) 84
b) 274
c) 120
d) 75
e) 66
5. Perform the indicated operations and give the answer in cm with the proper number of
significant figures.
a) 104.0
b) 103.95
c) 103.951
d) 104
e) none of these
6. Convert 55 miles per hour to meters per second (1 mile = 5280 ft; 1 m = 39.37 in).
a) 25
b) 88
c) 2.4 x 10-2
d) 3300
e) 42
7. The mass of 236 mL of the liquid, ethanol is found to be 186 g. What is the density of ethanol in
g/mL?
a) 1.27
b) 0.789
c) 1.00
d) 788
e) 0.00127
8. Taken by itself the fact that 8.0 g of oxygen and 1.0 g of hydrogen combine to give 9.00 g of
water demonstrates what natural law?
a) Conservation of Mass
d) The Atomic Theory
b) Constant Composition
e) Multiple Proportions
c) Periodicity
9. How many neutrons are in the nucleous of 232Th atom?
a) 232
b) 90
c) 81
d) 151
e) 142
10. Predict the product of the reaction of strontium, Sr with phosphorous, P.
a) Sr3P2
b) Sr2P3
c) SrP
d) SrP2
e) Sr2P
11. An Fe2+ ion contains:
a)
b)
c)
d)
e)
28 protons, 28 neutrons and 26 electrons
26 protons, 30 neutrons and 24 electrons
26 protons, 26 neutrons and 26 electrons
58 protons, 58 neutrons and 56 electrons
54 protons, 56 neutrons and 52 electrons
12. Naturally occurring lithium consists of two isotopes Li-6 and Li-7. The atomic mass of Li is
approximately 6.9. What are the reasonable estimate of the relative percentages of Li-6 and Li7, respectively?
a) 10, 90
b) 25, 75
c) 50, 50
d) 75, 25
e) 90, 10
d) S
e) Si
13. Which of the following would be a metal?
a) P
c) Se
d) Sr
14. Which of the following is molecular?
a) Fe2O3
b) NaOH
c) NF3
d) CuCl2
e) CdS
c) 208
d) 71.85
e) 271.39
15. Calculate the molar mass of Fe(III) oxide.
a) 183.4
b) 159.69
Part II. Calculations:
1. Calculate the number of moles of CO present in 125 g sample of the gas.
2. Calculate the number of molecules of CO2 present in 44.01 g sample of the gas.
3. Calculate the number of atoms in CO2 in the above problem.
4. What is the mass % of As in As2O3?
5. Calculate the number of atoms in 21.5 g of potassium.
6. How many moles are in 154.5 g of NiCO3?
7. How many moles are in 100. g of Arsenic?
8. What mass of titanium is equivalent to 5.25 g mols?
9. How many grams of Fe2(SO4)3 are in 2.5 moles?
10. An unknown compound contains the elements carbon, hydrogen and oxygen. Elemental
analysis shows that the compound is 47.52% carbon, 4.986% hydrogen and 47.49% oxygen.
Determine the simplest formula.
11. Dibutyl succinate is an insect repellent used against household ants and roaches. Its
composition is 62.58% C, 9.63% H, and 27.79% O. Its experimentally determined molar mass
was found to be 230 g/mol. What are the empirical and molecular formulas of dibutyl
succinate?
12. Vitamin C is essential for prevention of scurvy (and large doses may be effective in preventing
colds). Combustion of a 0.2000-g sample of this carbon-hydrogen-oxygen compound yields
0.2998 g CO2 and 0.0819 g H2O. What is the empirical formula of vitamin C?
13. Naturally occurring europium (Eu) consists of two isotopes. One of the isotopes has a mass of
159.960 amu and 48.03% abundance. What is the atomic mass of the other isotope?
______________________________________________________________________________
Part III.
Complete the table with the formula or name of the compound
Formula
Name
Ammonium nitrate
Dinitrogen pentoxide
Cobalt(III) sulfate
K3PO4
SF6
FeCl3
Sodium chlorate
Al2O3
Ca2N3
Hydrobromic acid
ANSWERS
Part I: 1) a
7) b
13) d
2) e
8) a
14) c
3) d
9) e
15) b
Part II: 1) 4.46 mols CO
3) 1.807 x 1024 atoms CO2
5) 3.31 x 1023 atoms K
7) 1.335 mols As
9) 1000 g Fe2(SO4)3
11) EF: C6H11O2 & MF: C12H22O4
13) 144.6 amu
Part III: 1) NH4NO3
4) Potassium phosphate
7) NaClO3
10) HBr (aq)
4) a
10) a
5) ?
11) b
6) a
12) a
2) 6.022 x 1023 molecules CO2
4) % As = 37.97
6) 1.302 mols NiCO3
8) 251 g Ti
10) C4H5O3
12) C3H4O3
2) N2O5
5) sulfur hexafluoride
8) aluminum oxide
3) Co2(SO4)3
6) iron(III) chloride
9) calcium nitride