Name
Chemistry 121
Prof. Mines
Practice Exam to Prepare for Exam 1a (25 points)
NOTE #1: Many of these questions WERE asked on a prior exam, although this “exam” was never
actually administered “as is”. This practice exam is designed to give you an idea of the format of my
exams and the “style” of questions I ask (some students have never seen “T/F with correction” questions,
for example), although the specific topics and questions on your exam will not be identical to those
on this one (see NOTE #2). I have changed the point totals on the problems to better reflect what your
Exam 1a will look like (sum is 25 points).
NOTE #2: This should provide good practice for the exam, but do realize that some topics on your
problem sets (and worksheets) may not be represented on this practice exam but are still “fair game” for
your Exam 1a. always use the problem sets (and worksheets) as your guide to what topics, concepts, and
skills you are responsible for on an Exam.
This exam consists of 7 questions (many with multiple parts) on three pages.
1) Please briefly scan through the whole exam to make sure that you have all the pages
(and so that you can make the best use of your time).
2) Do not spend too much time on any one problem in the first half of the test
period.
3) Do questions that you feel you can do quickly first and come back later to questions
you are unsure about.
4) Take notice of the point value of the problems to help you judge your time and efforts
(see chart below!).
5) Make sure to report all calculated values to the proper precision and show your work
(unless you are told otherwise).
6) Remember, don’t panic if you don’t immediately “see” the answer; allow yourself time
to analyze each problem! Good luck!
Problem
1
2
3
4
5
6
7
TOTAL
Type
Received/Possible
Mult. Choice
T/F
/4
/3
/5
/3
/2
/4
/4
Free
Response
/25
Page 1
1. Circle the correct answer (4 pts total) (1 point each)
(a) Which of the following is not best described as an observation?
i) High energy, positively charged particles fired at a thin film of gold are occasionally
deflected or even bounced back.
ii) All of the positive charge in an atom is located in the nucleus.
iii) Flashes of light appear when an alpha particle beam interacts with a certain screen.
iv) When water is exposed to a high voltage, bubbles are formed.
(b) If a sample of substance A has a greater density than a sample of substance B, then
i) The sample of A has a greater mass than sample B.
ii) The sample of A has a smaller volume than sample B.
iii) If both samples have a mass of 5 g, the sample of A will have a greater volume.
iv) All of the above.
v) None of the above
(c) Which do scientists believe is not true about a sample of a compound whose formula
contains the symbols H and N:
i) It will contain a fixed mass ratio of hydrogen to nitrogen.
ii) It will contain hydrogen molecules and nitrogen molecules.
iii) If the sample is divided into three parts, all parts will exhibit the same properties.
iv) It will contain a fixed ratio of hydrogen atoms to nitrogen atoms.
(d) Which of the following can properly be said about the Law of Conservation of Energy?
i) It describes what appears to be true when processes occur in nature.
ii) It was once a theory.
iii) It explains why energy is conserved in nature.
iv) It has been proven by scientists by years of study.
2. Write T (True) or F (False) for the following statements. If the statement is false correct
it by changing, dropping, or adding a few words (3 points in total; 1 point each)
a) Mass is the amount of space a sample of matter occupies.
b) A sample that can be separated by physical means into two elements is a compound.
c) The more precisely known quantity is the one that limits the precision in a calculated result
obtained from two measured quantities.
Free-Response Questions (18 points in total)
Page 2
[NOTE: The following problem involves concepts/topics from both PS1 (end) and PS2
(beginning), so I will include it on both the Ex 1a practice exam and the Ex 1b practice exam.]
3. (5 pts) Consider the following:
sucrose
(C12H22O11)
(i)
(ii)
(iii)
(iv)
No explanations are needed for this problem!
(a) In the table below, use the abbreviations to indicate which words properly describe the
sample (as a whole) represented by the corresponding “box”. There may be multiple
words that apply in each case: element (E), mixture (M), substance (S), compound (C),
heterogeneous (HET), homogeneous (HOM).
(i)
(iii)
(ii)
(iv)
(b) List all the boxes that contain at least one compound anywhere in the box. _____________
Ignore box (i) for the following two questions:
(c) Which box(es) contain(s) a liquid anywhere in the box?______________
(d) Which box(es) contain(s) a solid anywhere in the box?______________
(e) How many elements are in box ii? ___________ in box iii? ___________
(f) How many molecules are in box iii? ____________
(g) How many compounds are in box iii? ____________
4. (3 pts) (a) Measure the length of the shaded bar below as best as you can using the ruler
provided. Report the value properly in the following space:
___________ inches
1
2
3
4
5
6
(b) Which digit in your answer is the uncertain but significant one? (no explanation needed)
(c) What is the approximate uncertainty in your measurement (no explanation needed)
inches
Page 3
5. (2 pts) A child weighing 18 kg is suffering from iron deficiency. If the recommended dosage of
iron for kids is (4.5 mg Fe)/(kg of body weight), and the medicinal solution contains
(15 mg Fe)/(0.6 mL of medicine), how many mL of the medicine should be administered to this
child? (Hint: I suggest doing this in two parts and thinking about the meaning of the units!)
6. (4 pts) Perform the following calculations and report the resulting quantities with the proper
degree of precision and proper units. Show your work!
(a)  4.32 cm12.12 cm 0.33 cm =
(b) (3.44 x 104 mi) + (2.18 x 106 mi) =
(c)
158.824 g - 142.7 g 
1.35612 g/mL
(d) Report each of your answers in (a)-(c) in proper scientific notation, making sure not to
change the meaning of each quantity.
7. (4 pts) (a) How many L/hr is a flow rate (in an IV drip, e.g.) of 3.4 mL/min?
(b) A typical paper bag used for disposing of yard waste says it holds 30 gallons. A ultility
bag is advertised as being 10 ft3. Which has the larger volume, the paper bag or the
utility bag? How many times bigger is it? (1 in = 2.54 cm; 1 gal = 3.78 L; 1 cm 3 = 1
mL)