CHEMISTRY 161
PRATICE MIDTERM #1
OCTOBER 8, 2015
For Multiple Choice Questions Circle the Letter Before the Best Answer
1. Which of the following is not a pure substance?
a.
b.
air
nitrogen gas
c.
d.
oxygen gas
argon gas
2. In a demonstration of strong electrolytes, weak electrolytes, and non-electrolytes, Professor
Popsnorkle used a light bulb apparatus that showed solution conduction of electricity by the
brightness of the light bulb. When pure water was tested, the bulb did not light. When some
acetic acid was added to the water, the bulb burned dimly. When more acetic acid was added to
the solution, the bulb burned a little more brightly. In his frustration to make the bulb shine
brightly with acetic acid, Professor E. N. Tropy started over by testing the beaker of the pure
acetic acid. What was the result?
a.
b.
c.
d.
The bulb did not light.
The bulb burned dimly.
The bulb burned more than any of the others, but still not brightly.
The bulb burned brightly.
3. Which of the following represents a physical property of water?
a.
b.
c.
d.
Water boils at 100°C.
An electrical current decomposes water into hydrogen gas and oxygen gas.
Water reacts with iron metal to form “rust.”
Water reacts with carbon monoxide to form carbon dioxide and hydrogen gas.
4. The following measurements of the mass of an aspirin tablet were made by different students in
a lab. Which set is the most precise?
a.
b.
1.513 g, 1.503 g, 1.522 g
1.513 g, 1.511 g, 1.450 g
c.
d.
1.513 g, 1.459 g, 1.533 g
1.513 g, 1.517 g, 1.512 g
5. Which of the following represents the law of multiple proportions?
a.
b.
H2O and CO2
CO and NO
c.
d.
PF3 and PF5
SO2 and CO
6. Zinc has five naturally occurring isotopes. Which of the following is the most abundant
isotope?
a.
b.
64
66
Zn, 63.9291 amu
Zn, 65.9260 amu
c.
d.
67
Zn, 66.9271 amu
Zn, 67.9249 amu
68
7. What is the empirical formula for benzene (C6H6)?
8. One molecular form of elemental sulfur is a ring of eight sulfur atoms. As one molecule of this
element is burned to make sulfur trioxide, how many oxygen molecules are used?
9. When bottles of hydrochloric acid and ammonia are stored close together in the lab, a white
dusty film forms around the bottles. What would that material be? Write a balanced equation
supporting your answer.
10. Assume the following:
•
A car gets 20.2 mi/gallon of gasoline.
•
Gasoline has the chemical formula of octane: C8H18.
•
One liter of gasoline has a mass of 0.803 kg.
•
Gasoline is completely burned to carbon dioxide.
How many kg of CO2 are produced by a car driven 20,500 mi in one year?
11. Phthalocyanine is a large molecule used in printing inks and dyes for clothing due to its
insolubility in most solvents, its chemical stability, and its intense blue color. Its elemental
analysis showed that it consists of 74.69% C, 3.525% H, and 21.77 % N. It has a molar mass of
514.54 g/mol. What is the molecular formula for phthalocyanine?
12. A mass of 11.60 g of phosphoric acid was produced from the reaction of 10.00 g of P4O10 with
12.0 g water. What was the percent yield for this reaction and the mass of the excess reactant?
The balanced equation is worth 3 points.
13. Assuming that the density of water is 1.00 g/mL, what is the molar concentration of water
(molarity)?
14. A 526 mg dietary supplement of L-lysine (an amino acid, FW 146.2) required 68.4 mL of 0.100
M NaOH to reach the end point. How many protons were removed for each L-lysine molecule
in this titration?
15. Balance the following REDOX equation by the Oxidation number method.
Cr2O72- (aq) + Fe2+ (aq) → Cr3+ (aq) + Fe3+ (aq)
(acidic)
16. For the left column below give the correct name and give formulas for compounds on
the right column
Compound Name
a. HMnO4
Write Formula
a. Hydrosulfuric acid
b. CrO3
b. Bromine Dioxide
c. H2O
c. Nitrogen phosphide
d. HIO4
d. Chromium(IV) oxide
17. Balance the following REDOX equation by the half reaction method clearly showing
electrons lost and gained.
Ag(s)
+
CN -
+
O2
→
Ag(CN)2
-
(basic)
18. Find the volume of water necessary to dilute 125 mL of a 1.324 M HCl solution to
0.984 M HCl.
19. Find the mass of a molecule of water.