PRACTICE MATERIAL for Exam 3
Fall, 2020
CHEM 1103
Please use this as a diagnostic tool by testing yourself under test-like conditions. No food, no music, no looking stuff up
but simply use your exam calculator and a periodic table. Allow yourself about 3 minutes/question on an average and
then if you miss the problem you’ll know where to get back into your book and notes to practice some more!
1. Which of the following is NOT true?
a) The forces holding atoms together in compounds are called chemical bonds.
b) When atoms share valence electrons the bonds are called covalent bonds.
c) More than one compound can have the same molecular formula, but not the same empirical
formula; for example, C2H4 and C6H12.
d) Ionic compounds form when cations and anions interact with each other through electrostatic
forces called ionic bonds.
e) NH4NO3 contains both ionic and covalent bonds.
2. Which of the following gives the correct formula for the compound that would form between
the two elements?
a) Li3N
b) CaS2
c) SrBr
d) Al3O2
e) GaCl4
3. Which of the following have both ionic and covalent bonds?
1. NH4NO3
a) 2, 5
2. CH4
b) 2, 3, 5
3. CaCl2
c) 1, 4
4. Na3PO4
d) 3
4. Which of the following is NOT a correct name and formula?
a) Manganese(IV) oxide, MnO2
b) Dibromine pentoxide, Br2O5
c) CuSO3 copper(II) sulfite
d) CuHSO3 copper(II) hydrogen sulfite
e) Carbon tetrachloride, CCl4
5. Which of the following is named incorrectly?
a) SCl2 sulfur dichloride
b) AlBr3 aluminum bromide
c) Na3P trisodium phosphide
d) P4O10 tetraphosphorus decoxide
e) Co2O3 cobalt (III) oxide
6. Which of the following is true?
a) Na2PO4 is sodium phosphate
b) Co(NO2)2 is cobalt nitrite
c) Ba(IO)2 is barium iodite
d) FeSO4 ∙ 7H2O is iron(II) sulfate heptahydrate
e) K2Cr2O7 is potassium chromate
7. Which of the following is named incorrectly?
a) CuSO4 · 5H2O is copper(II) sulfate pentahydrate
b) Co3(PO4)2 · 8H2O is cobalt(III) phosphate octahydrate.
c) LiMnO4 is lithium permanganate
d) Mg3N2 is magnesium nitride.
e) NI3 is nitrogen triiodide
5. C2H2
e) 1, 3, 4
8. In the Lewis dot structure of CO2, the number of unshared pairs of electrons on the central atom is -----.
a) 1
b) 2 c) 3 d) 4 e) 0
9. What is the molar mass of calcium phosphate?
a) 87.05 g/mol
b) 215.21 g/mol
c) 310.18 g/mol
d) 279.21 g/mol
e) 246.18 g/mol
10. How many nitrogen atoms are in 76.3 g N2O4?
a) 5.54 × 1025
b) 8.28 × 1023
c) 9.99 × 1023
d) 4.59 × 1025
e) 4.99 × 1023
11. Which of the following has the largest mass?
a) 2.5 moles of nickel(II) sulfite
b) 344 g of sodium acetate
c) 125 mL of potassium chloride with a density of 2.7 g/mL
d) 2.0 moles of potassium carbonate
e) 4.2 x 1024 formula units of Li2S
12. What is the percent of phosphorus by mass in magnesium phosphate?
a)
b)
c)
d)
e)
23.6
56.0
53.4
25.0
11.8
13. A Freon leak in the air conditioning system of an old car releases 20 g of CF 2Cl2 per month.
What mass of chlorine does this car emit into the atmosphere each year?
a) 240 g Cl/yr
b) 141 g Cl/yr
c) 72.0 g Cl/yr
d) 121 g Cl/yr
e) 180 g Cl/yr
14. How many carbon atoms are in a 94.8µL sample of cyclohexanol (C6H12O)?
Its density is 0.962 g/ml.
a) 3.55 x 1021
b) 3.29 x 1024 c) 3.29 x 1021
d) 3.29 x 1023
e) 5.92 x 1020
15. What mass of aspartame, C14H18N2O5, contains 4.0 × 1010 atoms of nitrogen?
a) 10.2 pg
b) 9.8 pg
c) 1.3 pg
d) 0.15 pg
e) 890 pg
16. How many Mg2+ ions are in a 3.44 nanogram sample of magnesium phosphate Mg3(PO4)2?
a) 1.31x1011
b) 3.93x1011
c) 2.36x1013
d) 7.88x1012
e) 3.44x1012
17. How many hydrogen atoms are in 31.3 mL of ethanol (CH3CH2OH) if its density = 0.798 g/mL?
a) 150
b) 1.96 x 1024
c) 1.18 x 1024
d) 3.27 x 1023
e) 6.02 x 1023
18. What is the molecular formula of a compound that is 49.48% carbon, 5.19% hydrogen, 28.85% nitrogen,
and 16.48% oxygen? The molecular weight is 194.19 g/mol.
a) C8H12N4O2
b) C4H5N2O
c) C8H10N4O2
d) C8H10N2O
19. Combustion analysis of 63.8 mg of a compound containing C, H and O produced 145.0 mg of CO 2 and
59.38 mg of H2O. What is the empirical formula for the compound?
a) C5H2O
b) CHO
c) C3H6O
d) C3H7O
e) C6HO3
20. A 43.0 g sample of an organic compound containing carbon, hydrogen, and oxygen produces
85.90 g CO2 and 35.20 g H2O by combustion analysis. Find the molecular formula if the
molar mass = 88.0 grams.
a) C2H16O3
b) C4H8O2
c) C3H4O3
d) C5H12O
e) C3H18O2
21. Rank the following bonds by increasing polarity: 1. Ba-Cl
a) 3 ˂ 2 ˂ 4 ˂ 1
d) 3 ˂ 2 ˂ 1 ˂ 4
b) 2 ˂ 3 ˂ 1 ˂ 4
e) 1 < 4 < 2 < 3
2. N-O
3. Br-Br
4. Al-O
c) 1 ˂ 4 ˂ 3 ˂ 2
22. Which of the following is NOT true for the correct Lewis structure?
a) The cyanide ion has a triple bond.
b) The hypochlorite ion has a single bond.
c) The nitrite ion has one double and one single bond.
d) N2H2 would have a double bond between the nitrogens.
e) C2H2 would have a double bond between the carbons.
23. Consider a molecule with the following connections:
When a valid electron dot structure is written, how many double bonds will the molecule contain?
a) 0
b) 1
c) 2
d) 4
24. In the most acceptable electron-dot structure for carbonyl fluoride, COF2 the central atom is
a) O, which is singly-bonded to C
c) O, which is doubly-bonded to C.
b) C, which is doubly-bonded to O.
d) C, which is singly-bonded to O.
25. Which of the follow is NOT true for the Lewis structures?
a) The nitrogen atom in the ammonium ion has 4 bonds and no lone pairs.
b) N2H4 has a double bond and 4 single bonds.
c) C2H4 has a double bond and 4 single bonds.
d) The cyanide ion has a triple bond and two lone (nonbonding) pairs.
e) The hypobromite ion has 6 lone (nonbonding) pairs and one single bond.
26. Choose the best Lewis structure for NO3⁻.
a)
b)
c)
d)
e)
27. Which of the following is true?
a) In the most favorable Lewis structure for H2CO, there are 3 single bonds and 3 lone pairs of
electrons.
b) In the most favorable Lewis structure for HCOOH, the first oxygen atom is bonded to the carbon
atom and the second oxygen atom.
c) In the most favorable Lewis structure for C2H4, there are 5 single bonds and 1 lone pair of electrons.
d) In the most favorable Lewis structure for HCN, there is 1 single bond, 1 triple bond, and 1 lone pair
of electrons.
e) In the most favorable Lewis structure for CO, there is 1 double bond and 3 lone pairs of electrons.
28. Which of the following is true?
a) The most favorable Lewis structure for NO3– has 1 single bond, 2 double bonds, and 7 lone pairs of
electrons.
b)
c)
d)
e)
The most favorable Lewis structure for BrO3– has 3 single bonds and 10 lone pairs of electrons.
The most favorable Lewis structure for NH4+ has 4 single bonds and no lone pairs of electrons.
The most favorable Lewis structure for O22– has 1 double bond and 4 lone pairs of electrons.
The most favorable Lewis structure for ClO– has 1 double bond and 6 lone pairs of electrons.
29. Draw three resonance structures for cyanate, NCO–, where all of the atoms obey the octet rule.
Which of the following is true?
a) In the most favorable Lewis structure, there are 2 double bonds.
b) In the least favorable Lewis structure, there is a triple bond between carbon and nitrogen.
c) In the most favorable Lewis structure, there are 2 lone pairs of electrons on nitrogen.
d) In the most favorable Lewis structure, there are three lone pairs of electrons on oxygen.
e) In the least favorable Lewis structure, there are 2 lone pairs of electrons on oxygen.
30. Which of the following is true?
a) In the most favorable Lewis structure for SO32–, two of the bonds are double bonds.
b) In the most favorable Lewis structure for XeF4, there are 3 lone pairs of electrons on xenon.
c) In the most favorable Lewis structure for BeF2, there are 2 double bonds.
d) In the most favorable Lewis structure for NO, there is a triple bond.
e) In the most favorable Lewis structure for PO43–, there are 3 single bonds and 1 double bond.
31. For which of the following does the most favorable Lewis structure obey the octet rule for all atoms?
a) BeH2
b) ClF3
c) PCl3
d) BF3 e) XeCl2