CHM 50
1.
Class Activity – Chapter 2 – part 1
Name
Two unknown compounds are tested. Compound I contains 15.0 g of hydrogen and 120.0 g of oxygen.
Compound II contains 2.0 g of hydrogen and 32.0 g of oxygen. Are the compounds the same? Which law
does it follow?
2. Two different compounds are formed by the elements carbon and oxygen. The first compound contains
42.9% by mass carbon and 57.1% by mass oxygen. The second compound contains 27.3% by mass carbon
and 72.7% by mass oxygen. Show that the data are consistent with the Law of Multiple Proportions.
3. Label the information provided in the periodic table.
2. What does the atomic number represent?
____________________ or ____________________
3. What does the atomic mass represent?
____________________ + ____________________
4. How would you figure the number of protons or electrons in an atom?
5. How would you figure the number of neutrons in an atom?
6. Write isotopic symbols of the form
for each of the following isotopes
a. Sodium isotope with 12 neutrons
b.
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Iodine isotope with 74 neutrons
7. Complete the following table
Z
A
p+
n
e-
Isotopic symbol
16
17
63
29
74
56
8. Complete the table Isotope
Complete the table Isotope
Mass (amu)
Neon-20
19.992
Neon-21
20.994
Relative Abundance
(%)
90.51
Neon-22
9.22
Avg. Atomic Mass = 20.179
Total %: 100.00
9. A new element, Albanesium, has been discovered. 43.2% of all naturally occurring Albanesium has a mass
of 292 amu. 46.8% of all Albanesium has a mass of 293 amu. The rest of the Albanesium has a mass of
295 amu. Find the average atomic mass of Albanesium.
10. Explain why atoms have different isotopes. In other words, how is it that helium can exist in three different
forms?
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11. Complete the following table
Atom or ion
Number of protons
Number of electrons
Electrons lost/gained
K+
12
10
16
2 e- gained
28
12.
Convert to moles:
a. 12.04 x 1023 atoms He
2e- lost
13.
Convert to grams
10.0 moles Na
b.1 atom S
5.00 moles Ag
c.0.005 grams Cl2
14.
Convert to number of atoms:
a. 8.50 moles Ca
b. 0.001 moles Cd
c. 1.0 x 10-5 moles O2
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