Honors Chemistry
Mr. Trubic
Semester I Exam Review
Chapters 1−2 Assessment
Answer Key
Name ________________________________________
Date _____________________
Directions:
Read each question carefully and write your response in the space provided following each question. Your
responses to these questions will be scored on the basis of the accuracy and relevance of the information cited.
Explanations should be clear and well organized. Specific answers are preferable to broad, diffuse responses.
For calculations, clearly show the method used and the steps involved in arriving at your answers. It is to your
advantage to do this, since you may obtain partial credit if you do and you will receive little or no credit if you do
not. Pay attention to units and significant figures.
1. Use scientific notation to express the number 385,500 to
5
(a) one significant figure.
4 × 10
_______________________________
(b) two significant figures.
3.9 × 10
_______________________________
5
5
3.86 × 10
(c) three significant figures. _______________________________
5
3.855 × 10
(d) four significant figures. _______________________________
2. Would a car traveling at a constant speed of 65 km/h violate a 40 mi/h speed limit? Support your answer with
a calculation. (1 mi = 1.609 km)
! 65 km $!
$
1 mi
#
&#
& = 40. mi h
" 1 h %" 1.609 km %
No. The driver would be within the speed limit.
Honors Chemistry
Mr. Trubic
Semester I Exam Review
Chapters 1−2 Assessment
3. Complete the following table.
Protons
Neutrons
Electrons
Mg
12
12
10
63
28
28
35
28
34
45
36
24
12
79
34
2+
Ni
Se
2−
4. An element consists of four naturally occurring isotopes, as shown in the table below. Calculate the atomic
mass, in amu, and identify the unknown element.
Isotopic Mass (amu)
Percent Abundance
203.97
1.40%
205.97
24.10%
206.98
22.10%
207.98
52.40%
(0.0140)(203.97 amu) =
2.86 amu
(0.2410)(205.97 amu) =
49.64 amu
(0.2210)(206.98 amu) =
45.74 amu
(0.5240)(207.98 amu) =
109.0 amu
Total
207.2 amu
The element is lead, Pb.