CP Chemistry
Unit 1 Test Review KEY
Problems and questions:
1. Round each of the following numbers to 3 significant figures:
a) .09882 .0988
b) 123,459 123,000
c) 102.45 102
d) 2.301 x 10-3
2.30 x 10-3
2.
Calculate, use sig figs: (12.22 x 14.02 x 120.1 x .555) / 10.00 =
3.
A sample of metal having a mass of 12.122 g is added to a graduated cylinder containing 35.2 mL of water. The water level
rises to 38.4mL. Calculate the density, use correct significant figures.
𝒅=
4.
1140
𝟏𝟐. 𝟏𝟐𝟐
= 𝟑. 𝟖 𝒈/𝒎𝑳
𝟑. 𝟐
What is the % difference between the following numbers: .0045 and .0038?
%𝒅𝒊𝒇𝒇𝒆𝒓𝒆𝒏𝒄𝒆 =
|. 𝟎𝟎𝟒𝟓−. 𝟎𝟎𝟑𝟖|
× 𝟏𝟎𝟎 = 𝟏𝟔. 𝟗%
(.𝟎𝟎𝟒𝟓+.𝟎𝟎𝟑𝟖
)
𝟐
5.
Write the symbol for the following ions: Mg losing 2 e-, Al losing 3 e-, N gaining 3 e-, S gaining 2 eMg2+, Al3+, N3-, S2-
6.
List three points of Dalton’s atomic theory.
A. Elements made of tiny particles, called atoms
B. Atoms of a given element are identical; the atoms of different elements are different.
C. In chemical reactions, atoms are combined, separated, or rearranged. Atoms cannot be
subdivided, created, or destroyed.
D. Atoms combine with atoms, in small whole numbers, to form compounds.
7. Describe Thompson’s experiment with the cathode ray tube, what did he discover?
Cathode ray tube consists of a cathode (negative) and anode (positive) side. The “ray” could be bent with magnetic or
electric fields. The “ray” bent toward a positive EM field and away from a negative EM field. Discovered electron and
charge to mass ration of electron.
8. Describe Millikan’s Oil Drop experiment. What exactly did he determine?
He suspended a micro oil droplet in an electric field and was able to determine the actual charge of an electron to be -1.6
x 10-19 C. Also, determined the mass of an electron.
9. Explain Rutherford’s Gold Foil experiment. What were three observations and three conclusions?
He fired alpha particles at fold foil and observed: 1) most went straight through, 2) small number showed a slight
deflection, 3) very few bounced straight back. He concluded: 1) mass of atom is in the nucleus, 2) nucleus is positively
charged, 3) atom mostly empty space.
10. What is an isotope? Atoms of the same element that differ by # of electrons.
11. Write the symbol of the most abundant copper isotope if the average atomic mass is 63.55? 𝟔𝟒
𝟐𝟗𝑪𝒖
12. Write the nuclear symbol for an isotope with Z=40, and 45 neutrons? 𝟖𝟓
𝟒𝟎𝒁𝒓
13. Consider the diagram and match the letters with the correct decay particle
A= beta particle, B= gamma, C= alpha or positron
14. For the types of radiation given, which is the correct order of increasing ability to penetrate matter?
(A)  <  < 
(B)  <  < 
(C)  <  < 
(D)  <  < 
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15. Place the forms of hydrogen (H, H+, H-, H2) in the table.
Atom
Cation
Anion
H
+
H
H
16.
Molecule
H2
Symbol
Mass (amu)
Mass in (g)
Charge
Location
Who Discovered
proton
p+
1
1.67 x 10-24 g
1
nucleus
Rutherford
neutron
n0
1
1.67 x 10-24 g
0
nucleus
Chadwick
electron
e-
0
9.11 x 10-28 g
-1
nucleus
Thompson
17. Where does the positron come from in positron emission? What is the other particle produced? proton changing into a
neutron plus a positron.
18. What are protons and neutrons made of? combinations of quarks.
19. What is the unit used to measure masses of atoms and what is it based upon? the atomic mass unit (amu) is based on 1/12
the mass of a C-12 isotope.
20. What is the proton to neutron ratio for the following isotope Te-110. Do you think this isotope is stable?
58 𝑛𝑒𝑢𝑡𝑟𝑜𝑛𝑠
110-52= 58 neutrons,
= 1.12, so ratio is 1:1.22. Isotope probably not stable due to the ratio being> 1:1
52 𝑝𝑟𝑜𝑡𝑜𝑛𝑠
21. What type of subatomic particle is an electron? An electron is actually a type of Lepton.
22. Describe the two forces involved in containing protons and neutrons in the nucleus of an atom.
The electromagnetic force is responsible for the protons in a nucleus repelling, the range is infinite. The strong
nuclear force attracts protons and neutrons, but it has a very short range force.
23. Why does an unstable nucleus decay? A nucleus is unstable because the strong nuclear force is not able to hold the
nucleus together. This can happen if the proton to neutron ration is greater than 1:1 or if the nucleus is larger than Z
=83.
24. What is the difference between fission and fusion? Use nuclear reactions to illustrate your answer. Fusion is the
combination of two light nuclei such as hydrogen or helium to make a larger atom, with a release of enormous
amounts of energy (recall mass defect). Fission is the splitting of large nuclei such as U-235 into smaller fragments,
with a release of large amounts of energy.
25. Why is C-14 used to determine that age of artifacts? All living organisms contain C-14 with a half life of 5730 years.
For the following write balanced nuclear reactions.
26.
180
53
I undergoes positron emission
27.
214
83𝐵𝑖
28.
137
60
Nd produces an alpha particle
29.
170
80
Hg
30.
196
92
31.
214
82
undergoes beta decay
180
53𝐼
214
83𝐵𝑖
→
0
−1𝑒
137
60𝑁𝑑
+
180
52𝑇𝑒
214
84𝑃𝑜
→ 42𝐻𝑒 +
undergoes positron decay
→ 42𝐻𝑒 +
214
82𝑃𝑏
133
58𝐶𝑒
170
80𝐻𝑔
undergoes beta emission plus gamma
U produces an alpha particle 196
92𝑈
Pb
→ 01𝑒 +
→
0
−1𝑒
+
170
81𝑇𝑙
+ 00𝛾
192
90𝑇ℎ
→ 01𝑒 +
214
81𝑇𝑙
2
231
90𝑇ℎ
32. Th-231 decays to Pa-231
33. Th-232 decays to Ra-228 particle
34.
32
15𝑃
35.
187
75𝑅𝑒
232
90𝑇ℎ
→
231
91𝑃𝑎
→ 42𝐻𝑒 +
+
0
−1𝑒
228
88𝑅𝑎
99
38𝑆𝑟
36.
37. 1 H + 1 H
1
2
® ___+ 01n
38. The half-life of
𝑵 = (𝟓𝟎𝟎). 𝟓
210
83
𝟏𝟎
2
2𝐻𝑒
Bi is 1.0 year. If you begin with 500g of this isotope, how many grams will you have left 1 decade later
= . 𝟒𝟗𝒈
39. The half-life of francium is 21 minutes. Starting with 4x1018 atoms of francium, how many atoms would
disintegrate in 1 hour and 45 minutes? What fraction of the original sample remains?
105
21
N = (4x10 ).5
18
=1.25x1017
40. An ancient piece of cloth was discovered at an archaeological site and it contained only 1.5625% of the C-14 as compared to
a similar sample from today. How old is this cloth if the half-life of C-14 is 5730 years
100% --- 50%---25%---12.5%---6.35%---3.125%---1.5625% 6- ½ lives (5730)=34,380 years.
41. If 87.5 % of a sample of pure Pb-210 decays in 36 days, what is the half-life of Pb-210?
100---50---25---12.5; if only 12.5% remains that means 87.5% has decayed. 36 divided by 3 ½ lives, is 12 days.
42. Calculate the average atomic mass of the following atom:
Zn-64 63.95 amu
38.25%
Zn-65 64.02 amu
6.25%
Zn-66 65.22 amu
55.50%
(63.95x.3825) + (64.02x.0625) + (65.22x.555)= 64.66 amu
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