Chem 120 Practice Midterm Examination
This practice test lists several possible questions and resembles the actual test on Friday. You
should look at the exam 1 study guide. You will have a similar page with conversion factors etc.
at the exam. The first problem is multiple choice. Be sure to choose only ONE answer for each
part. This is a closed book exam. You may use a calculator, but it must be a calculator – not a
phone, computer, music player, etc. You may not have an internet connection open at any time.
Report numerical answers to the correct number of significant digits and with the units clearly
specified. SHOW YOUR WORK
1. Multiple choice problems. Two points each. Put your best answer in the box. DO NOT
GUESS. Each incorrect answer will result in subtraction of two points.
.
a.
Which of the following is the smallest mass?
A. 4.0 x 10-6 g
B. 4.0 x 109 ng.
C. 4.0 x 10-2µg
D. 4.0 x 10-3kg
E. 4.0 x 10-9 mm.
b.
The number of significant figures in the measurement of 45.030 mm is
A. two
B. three
C. four
D. five
E. six
c.
When 2610 + 11.7 + 0.22 are added, the answer is
A. 2621.92
B. 2621.9
C. 2621
D. 2620
E. 2600
d.
Absolute zero is
A. the freezing point of water on the Celsius scale
B. the boiling point of liquid oxygen
C. the temperature on the Kelvin scale corresponding to 32 °F
D. the coldest temperature possible
E. the freezing point of liquid nitrogen.
e.
Which of the following elements is a noble gas?
A. oxygen(O)
B. nitrogen(N)
C. chlorine(CL)
D. neon(Ne)
E. None of the above
f.
The smallest sample of an element that retains the characteristics of the element is a(n)
A. electron
B. atom
C. neutron.
D. one gram
E. proton
g.
The atomic number of an atom is equal to the
A. number of neutrons
B. number of protons
C. number of protons plus neutrons
D. number of protons plus electrons
E. None of the choices A-D
h.
An element has the electron configuration 1s22s22p63s1. Which element is it?
A. sodium
B. barium
C. argon
D. potassium
E. None of the choices A-D are correct
2. The LD50 values for some chemicals are listed below:
Capsaicin
Nicotine
Ibuprofen
LD50 (mg/kg body mass)
47
50
490
a. Which substance has the lowest toxicity? (circle one)
Capsaicin
Nicotine
Ibuprofen
b. If one cigar contains 10 mg of nicotine, calculate the number of cigars required to achieve
a 50% lethal dose for a person weighing 125 pounds.
3.
a. What physical process is represented by the region labeled W?
b.
Data for four materials is given above. Which material corresponds to the heating curve
in part a?
c. Specify the phase(s) present at point Y in the diagram from a.:
Solid
liquid
gas
4. A 50:50 mixture of ethylene glycol and water is used as antifreeze. This mixture melts at
-30 °F and boils at 225 °F. Given the data below, find the amount of energy (in Joules), which
must be removed from 0.50 pounds of antifreeze to cool it from 80 °F to -150°F.
5. Boron(B) has two isotopes. A particular sample was found to have the following isotopic abundances:
a. Write the isotope symbol for the two isotopes of boron, including mass number and atomic
number.
b. Calculate the atomic mass of boron in this sample. Show your work