Name
Chemistry 121
Prof. Mines
Practice Exam to Prepare for Exam 1b [PS2 & PS3 material] (50 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 1b will look like (sum is 50 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 1b. 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 10 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
8
9
10
TOTAL
Type
Received/Possible
Mult. Choice
T/F
/3
/4.5
/5
/5
/13.5
/4
/2.5
/4
/3.5
/5
Free
Response
/50
Page 1
1. Circle the correct answer (3 pts total) (1.5 points each)
(a) Which of the following is the most dense (has the highest density):
i) a 1-mL airtight container with exactly one atom of nitrogen in it (and nothing else)
ii) a nitrogen atom (as a whole)
iii) the nucleus of a nitrogen atom
iv) more information is needed
(b) “Mass number” is:
i) the mass of the protons and neutrons in a given atom
ii) the mass of an atom of an isotope
iii) the number of protons in the nucleus of a given atom
iv) the non-integer number found in the box of an element on a periodic table
v) none of the above
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 (4 points in total; 1 points each)
a) A sample of a molecular compound is composed of identical neutral entities called
molecules, and a sample of an ionic compound is composed of identical entities called
cations.
b) Cations are formed when atoms lose one or more electrons, but atoms of O gain two
electrons each when they form oxide ions.
c) A nitrogen atom has an average atomic mass of approximately 14.0 g.
Free-Response Questions (78 points in total)
3. (5 pts) (a) What makes a gold atom be a gold atom and an atom of aluminum be an atom of
aluminum? (The symbol for gold is Au and the symbol for aluminum is Al.)
(b) Keeping in mind your answer to (a) answer the following. If Rutherford had used a thin
film of aluminum rather than gold for his experiments in which he directed a beam of highenergy, positively charged alpha particles at a thin metal foil, would you predict that the
fraction of alpha particles deflected would have been (circle one): (i) smaller, (ii) greater, or
(iii) about the same? Describe your reasoning in a brief paragraph.
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.]
4. (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? ____________
5. (13.5 pts) Fill in the blanks in the following table (1.5 pt each).
Proper Chemical Formula
Na2HPO4
HNO2
Cl2S4
Pb(IO)4
(circle one to name) CrO or Cr2O3
Systematic Name
calcium sulfite
potassium carbonate
bromic acid
aluminum perchlorate
6. (4 pts) Write the chemical formula for the following:
(a) the compound composed of Ru3+ and CrO42- ions:
(b) the compound formed from Cs and P:
Page 3
7. (2.5 pt) (a) Identify the the type of nanoscopic entities (basic units)—atoms, molecules, or
ions—that make up a macroscopic sample of the following (no explanation needed):
(i) NH4F
(ii) Cu
(iii) NO2
(iv) O2
(v) Na2S
8. (4 pts) (a) Draw nanoscale pictures depicting a sample of five formula units of NO2 as a solid
(left), and then after it has turned into a gas (right).
“N” =
“O” =
sublimation
9. (3.5 pts) (a) How many (i) protons and (ii) neutrons are in an atom of
how you obtained your answers.
131
I? Briefly make clear
(b) Write the complete symbols (i.e., a proper superscript and subscript in the proper places)
for any two possible isotopes of bromine (do not worry if these isotopes actually exist).
10. (5 pts) (a) Complete the folowing table.
(NOTE: This problem came from a former problem set [Zumdahl text], not an exam of mine. This explains the repetition,
which would not generally appear on a timed exam of mine. –Prof. Mines)
Number of
Protons (p)
Number of
Neutrons (n)
(ii)
20
24
(iii)
23
28
20
(v)
35
44
36
(vi)
15
16
Symbol
(i)
(iv)
235
92
90
39
Number of
Electrons (e)
Net Charge
U
2+
Y
3-
(b) Which of the elements in part (a) are metals? nonmetals? metalloids (semimetals)?