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
Calculate the % error for an experiment where the student measured 3.45 g and the actual value was 3.00 g?
%𝒆𝒓𝒓𝒐𝒓 =
|𝟑. 𝟒𝟓 𝒈−. 𝟑. 𝟎𝟎𝒈|
× 𝟏𝟎𝟎 = 𝟏𝟓. 𝟎%
(𝟑. 𝟎𝟎𝒈)
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.
7.
a) 2 b) 3 c) 12 d) 5
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.
8. 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.
9. 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.
10. 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.
11. What is an isotope? Atoms of the same element that differ by # of electrons.
12. Write the symbol of the most abundant copper isotope if the average atomic mass is 63.55? 𝟔𝟒
𝟐𝟗𝑪𝒖
13. Write the nuclear symbol for an isotope with Z=40, and 45 neutrons? 𝟖𝟓
𝟒𝟎𝒁𝒓
14. Consider the diagram and match the letters with the appropriate particle
A= electron, B= neutron, C= proton
15. Place the forms of hydrogen (H, H+, H-, H2) in the table.
Atom
Cation
+
H
H
Anion
H
Molecule
H2
1
16.
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.
mass
molar mass
# moles
#atoms, molecules
2.50 g NH3
17.04 g/mol
0.15 moles NH3
8.8x1022 molecules NH3
55.85 g/mol
0.50 moles Fe atoms
3.01x1023 atoms Fe
3.07 moles CO2
1.85x1024 molecules CO2
27.93 g Fe
44.01 g/mol
135.25 g CO2
18. sdf
Z
CO2
𝐴
𝑍𝑋
A
p+
n0
e-
23
43
23
20
23
43
23𝑉
35
71
35
36
35
71
35𝐵𝑟
15
31
15
16
15
31
15𝑃
symbol
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. 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.
21. The electromagnetic force is stronger than the strong nuclear force and the nucleus breaks apart releasing radiation.
22. The half-life of
210
83
Bi is 1.0 year. If you begin with 500g of this isotope, how many grams will you have left 1 decade later
𝑵 = (𝟓𝟎𝟎). 𝟓𝟏𝟎 = . 𝟒𝟗𝒈
23. 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
24. 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.
25. 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
2
3
4
5