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CHE1031
CHE1031 Chapter 2 Practice Problems
These examples can be used with tutors or during help sessions.
Atomic Theory of Matter
1. A chemist finds that 30.82 g of nitrogen will react with 17.60 g, 35.20 g, 70.40 g or 88.0 g of
oxygen to form four different compounds.
a. Calculate the mass of oxygen for each gram of nitrogen in each compound.
b. How do the results of your calculations for part a) support Dalton’s atomic theory?
Discovery of Atomic Structure
2. A charged particle is shot through two electrically charged plates as shown below.
a. Why does the particle’s path bend?
b. What is the charge of the particle, + or - ?
c. If the charge on the plates is increased will the degree of bending change? If so, how?
d. If the mass of the particle is increased but the speed is unchanged, will the degree of
bending stay the same, increase or decrease?
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Modern View of Atomic Structure
3. The diameter of a dime is 17.9 mm. The diameter of an Ag atom is 2.88 Å. How many silver
atoms can fit across the diameter of a dime?
4. A cube of gold that is 1.00 cm on each side has a mass of 19.3 g. A single gold atom has a
mass of 197.0 amu.
a. If 5.90 x 1022 atoms of gold are in the cube, calculate the diameter of one gold atom.
b. What assumptions did you make to answer b?
Atomic Numbers, Mass Numbers & Isotopes
5. How many protons, neutrons & electrons are there in these atoms:
a. 40Ar
b. 65Zn
c. 70Ga
6. How many protons, neutrons & electrons are there in a 138Ba atom?
7. How many protons, neutrons & electrons in an atom of 31P?
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CHE1031
8. Magnesium has three isotopes with mass numbers 24, 25 and 26.
a. Write the chemical symbol (with super- and subscripts) for each isotope.
b. How many neutrons are there in each of those isotopes?
Atomic Weight
9. A particular atom of chromium has a mass of 52.94 amu. But the atomic weight of
chromium is 51.99. How can that be? What’s the explanation?
10. Three isotopes of silicon occur in nature: 28Si (92.23%) with an atomic mass of
27.97693amu; 29Si (4.68%) with an atomic mass of 28.97649 amu; and 30Si (3.09%) with an
atomic mass of 29.97377 amu. Calculate the average atomic mass of silicon.
The Periodic Table
11. Match these elements with their descriptions: Ar, H, Ga, Al, Ca, Br, Ge, K, O
a. alkalai metal
b. alkaline earth metal
c. noble gas
d. halogen
e. metalloid
f. nonmetal in group IA
g. metal whose ion has a +3 charge
h. nonmetal whose ion has a -2 charge
i. element that resembles Al
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Molecules & Chemical Formulas
12. How many?
a. carbon atoms in C2H5COOCH3
b. oxygen atoms in Ca(ClO4)2
c. hydrogen atoms in (NH4)2(HPO4)
13. Write the empirical formulas of these molecular compounds:
a. Al2Br6
b. C8H10
c. C4H8O2
Ions & Charges
14. A particle has 16 protons, 16 neutrons and 18 electrons. Is it an atom, a cation or an anion?
15. What are the charges of the most stable ions formed by these elements:
a. Mg
b. Al
c. F
Ionic Compounds
16. What are the charges of the metal ions in each of these compounds?
a. NiO
b. MnO2
c. Cr2O3
Naming Compounds
17. Label each compound as molecular or ionic?
a. PF3
b. NaI
c. SCl2
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Ionic Naming
18. Give the names and charges of the cation and anion in each of these ionic compounds:
a. CaO
b. Ag2(SO4)
c. Al(ClO3)3
Molecular Naming
19. Give the name or formula, as appropriate.
a. SF6
b. IF5
c. tetraphosphorous hexasulfide
20. The oxides of nitrogen are very important components of urban air pollution. Name each:
a. N2O
b. NO
c. NO2
Naming Acids
21. Give the names or formulas of these acids, as appropriate:
a. H(BrO3)
b. H3(PO4)
c. hypochlorous acid
Naming Reviews
22. Gives the names of these common chemicals:
a. NaCl, table salt
b. Na(HCO3), baking soda
c. Na(ClO), in bleaching products
23. Many names and formulas are easily confused. So try writing formulas or names for each
of these pairs:
a. calcium sulfide vs. calcium hydrogen sulfide
b. hydrobromic acid vs. bromic acid
c. aluminum nitride vs. aluminum nitrite
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