OBJECTIVES: EXAM #3
SPRING, 2017
Quantitative Analysis
1. Recognize the importance of vitamin C for animal life and know what the RDA for vitamin C.
2. Determine the amount of vitamin C in known sample of juice using the chemical reaction of
vitamin C with iodine.
3. Know how heating affects Vitamin C and what manufacturers do to control the amount of
vitamin C there is in their juice.
4. Given a known amount of vitamin C in a sample determine how much juice would be needed
to obtain the RDA of vitamin C.
5. Given a known volume of juice determine the amount of vitamin C consumed.
Composition of Seawater
1. Know the approximate salinity (grams / liter, ppt) for typical seawater.
2. Know how the density of the water affects the buoyancy of an object floating in it.
3. Use data and plot a best-fit line to determine the salinity of a sample of seawater.
4. Describe how salinity, pressure and temperature affect the density of water.
5. Define thermocline, pycnocline, and halocline.
6. Describe an estuary.
7. Describe the interaction of fresh and salt water within an estuary.
Chemical Composition
1. Distinguish between an element, compounds, atom, and molecule.
2. Given a chemical reaction, identify each in a chemical formula or chemical reaction.
3. Distinguish the differences between a chemical change and a physical change and give an
example of each.
4. Balance a chemical reaction (same number of atoms on each side of an equation).
5. Identify common diatomic molecules especially those involved in the electrolysis of water.
6. Know the positive tests for the presence of hydrogen gas and oxygen gas.
7. Given a mixture of hydrogen and oxygen, predict the amount and type of gas left within (if
any) the container when ignited to produce water.
8. Calculate the percent composition of an element when presented with the chemical formula
of the molecule.
9. Know which gas is produced at each electrode during the electrolysis of water.
10. Distinguish between a conducting and non-conducting molecule based on its elemental
composition and their position within the periodic table.
11. Identify acids based on their chemical formula and why acids conduct electricity.
Acids and Bases
1. Define an acid and a base.
2. Identify the common characteristics of acids and bases.
3. List 3 acids and 3 bases and know their chemical formulas.
4. Given the pH of a solution, determine the concentrations of [H+] and [OH-].
5. Define an indicator and give an example.
6. Using the fact that pH is a logarithmic scale, compare the concentrations of [H +] in two
solutions with different pH.
7. Explain how acid rain is produced and why it is so harmful to the environment.
8. Know the pH’s of common household products.
9. Given the pH of two solutions, determine if they are able to form a neutral solution when
mixed.
Review
1. When evaporation at the ocean surface exceeds precipitation, what happens to the salinity of
seawater. Increases
2. Compare open ocean water near the equator and open ocean water in the North Atlantic.
Higher salinity at surface (equator), greater density due to lower temperature (NA)
3. Explain the effects of precipitation, freezing, and evaporation on the salinity of seawater.
(See laboratory)
4. In open ocean water, where does the water have a greater salinity, near the surface or near
the bottom? Provide an explanation for your answer. (Surface due to evaporation)
5. In open ocean water, where does the water have a greater density, near the surface or near
the bottom? Provide an explanation for your answer. (Bottom, due to lower temperature)
6. Describe the structure and usage of the Plimsol Line on a cargo vessel. (See laboratory)
7. On average, what is the concentration (in parts per thousand) of salt in open ocean water
world wide? (28 ppt)
8. The analysis of a sample of Orange Juice indicates that 25.0 mL of juice contains 5.5 mg of
Vitamin C. How much Vitamin C is there in a 350 mL glass of juice? (77 mg)
9. How much juice must be consumed to get the RDA of the Vitamin C (60 mg)? (273 mL)
10. What is a positive test for the presence of starch? (Iodine turns starch purple)
11. What is a positive test for oxygen gas? Hydrogen gas? Carbon dioxide? (See lecture quiz)
12. 15 mL of oxygen gas is mixed with 10 mL of hydrogen gas. The two are allowed to react to
form water vapor. At the end, what gas (oxygen or hydrogen) is remaining in the test tube and
how much of that gas remains? (10 mL O2)
13. Write a balanced chemical reaction for the electrolysis of water. (See lecture quiz)
14. In lecture I had one balloon filled with Hydrogen gas, and one balloon is filled with Oxygen
gas. Just by examining the balloons, how can you distinguish one gas from the other?
(See lecture quiz)
15. When water is boiling, what is inside the bubbles? During the electrolysis of water, what’s
inside the bubbles? Why do each of these processes produce different results?
Electrolysis breaks Intramolecular bonds and boiling breaks Intermolecular bonds.
16. Which of the following represent a physical change and which represents a chemical change?
tearing a sheet of paper P burning a candle C
using a battery to light a bulb C
boiling water P
chewing a candy bar C
digesting a candy bar C
17. You pulverize a 100. mg tablet of vitamin C and mix it with 100. mL of distilled water. You
extract a 10.0 mL sample and dilute this to 100 mL with distilled water. You now add a starch
indicator and find you need to add 10.8 mL of iodine solution to get a permanent color
change.
You now perform this experiment with orange juice. You take 25.0 mL sample of orange juice
and dilute it to 100.0 mL with distilled water. You add the starch indicator as before and find
you need to add 8.6 mL of iodine solution to this sample to get a purple color. (Show your
work and clearly label your answers)
a. How many mg of vitamin C are in this sample of orange juice? (7.96 mg)
b. How many mg of vitamin C are in an 8.0-oz (240 mL) serving? (191 mg)
c. How much juice do you need to drink for the RDA of 60 mg of vitamin C? (75 mL)
18. What determines if a solution conducts electricity or not? (Ionization)
19. Peanut M & M (Pe) and plain M & M (Pl) candies will be used to make candy “molecules”
which form when the two candy “elements” combine. The elements Pe and Pl are found pure in
nature only as diatomic molecules. They can combine to form a new candy compound with the
“chemical formula” of PePl3. Fifty-one plain (Pl) candies come in a bag and 21 peanut (Pe) candies
come in a bag.
a. How many molecules of Pe2 and Pl2 can be formed from the candies in the bag?
(25 Pl2 – 10 Pe2)
b. Write a balanced chemical reaction for the formation of PePl3.
3 Pl2 + Pe2
2 PePl3
c. From the molecules of Pe2 and Pl2 formed, how many molecules of PePl3 could be
constructed from your sample? (16 PePl3)