Name: _________________
Spting Recess Take-Home Exam
Base your answers to questions 1 and 2 on the information below.
The active ingredient in the pain reliever aspirin is acetylsalicylic acid. This compound can be produced
by reacting salicylic acid with acetic acid. The label of one aspirin bottle indicates that the accepted mass of
acetylsalicylic acid in each tablet is 325 milligrams.
In a laboratory, an aspirin tablet is crushed and mixed with water to dissolve all of the acetylsalicylic acid.
The measured pH of the resulting solution is 3.0.
1. The mass of acetylsalicylic acid in one aspirin tablet is determined to be 320. milligrams. Show a numerical
setup for calculating the percent error for the mass of acetylsalicylic acid in this aspirin tablet.
2. State the color of methyl orange indicator after the indicator is placed in the solution.
3. Base your answer to the following question on the information below and on your knowledge of chemistry.
Two very stable compounds, Freon-12 and Freon-14, are used as liquid refrigerants. A Freon-12
molecule consists of one carbon atom, two chlorine atoms, and two fluorine atoms. A Freon-14 molecule
consists of one carbon atom and four fluorine atoms.
Draw a structural formula for Freon-12.
4. Base your answer to the following question on
the information below.
Archimedes (287–212 BC), a Greek inventor and mathematician, made several discoveries important
to science today. According to legend, Hiero, the king of Syracuse, commanded Archimedes to find out
if the royal crown was made of gold, only. The king suspected that the crown consisted of a mixture of
gold, tin and copper.
Archimedes measured the mass of the crown and the total amount of water displaced by the crown
when it was completely submerged. He repeated the procedure using individual samples, one of gold,
one of tin, and one of copper. Archimedes was able to determine that the crown was not made entirely of
gold without damaging it.
Determine the volume of a 75-gram sample of gold at STP.
5. Write one electron configuration for an atom of silicon
in an excited state.
6. Base your answer to the following question on
the information below and on your knowledge of chemistry.
The pH of various aqueous solutions are shown in the table below.
State how many times greater the hydronium ion concentration in the HCl(aq) is than the hydronium ion
concentration in the HC 2H3O2(aq).
7. Base your answer to the following question on the information below.
In a titration, 3.00 M NaOH(aq) was added to an Erlenmeyer flask containing 25.00 milliliters of
HCl(aq) and three drops of phenolphthalein until one drop of the NaOH(aq) turned the solution a
light-pink color. The following data were collected by a student performing this titration.
Initial NaOH(aq) buret reading: 14.45 milliliters
Final NaOH(aq) buret reading: 32.66 milliliters
Show a correct numerical setup for calculating the molarity of the HCl(aq).
Base your answers to questions 8 and 9 on the
information below.
8. Explain, in terms of intermolecular forces, why ammonia
has a higher boiling point than the other compounds in
the table.
9. Explain, in terms of molecular polarity, why hydrogen
chloride is more soluble than methane in water at 20.ºC
and standard pressure.
10. Given the balanced equation:
4Al(s) + 3O 2(g)
2Al 2O3(s)
What is the total number of moles of O 2(g) that must
react completely with 8.0 moles of Al(s) in order to
form Al 2O3(s)?
11. Base your answer to the following question on
the information below and on your knowledge of chemistry.
Starting as a solid at –25°C, a sample of H2O is heated at a constant rate until the sample is at
125°C. This heating occurs at standard pressure. The graph below represents the relationship between
temperature and heat added to the sample.
Explain, in terms of heat of fusion and heat of vaporization, why the heat added during interval DE is
greater than the heat added during interval BC for this sample of water.
Base your answers to questions 12 and 13 on the information below.
Heat is added to a 200.-gram sample of H2O(s) to melt the sample at 0°C. Then the resulting H2O( ) is
heated to a final temperature of 65°C.
12. In the space below, show a numerical setup for calculating the total amount of heat required to raise the
temperature of the H2O( ) from 0°C to its final temperature.
13. Determine the total amount of heat required to completely melt the sample.
14. Base your answer to the following question on the information below.
Nitrogen gas and oxygen gas make up about 99% of Earth's atmosphere. Other atmospheric gases
include argon, carbon dioxide, methane, ozone, hydrogen, etc.
The amount of carbon dioxide in the atmosphere can vary. Data for the concentration of CO2(g) from 1960
to 2000 are shown in the table below.
Show a numerical setup for calculating the mass of carbon dioxide in a 100.0-gram sample of air taken in
1980.
15. The dissolving of solid lithium bromide in water is represented by the balanced equation below.
Based on Table F, identify one ion that reacts with
compound.
ions in an aqueous solution to form an insoluble
Base your answers to questions 16 through 18 on the information below.
A sample of helium gas is in a closed system with a movable piston. The volume of the gas
sample is changed when both the temperature and the pressure of the sample are increased. The table
below shows the initial temperature, pressure, and volume of the gas sample, as well as the final
temperature and pressure of the sample.
16. Compare the total number of gas particles in the sample under the initial conditions to the total number of
gas particles in the sample under the final conditions.
17. In the space below show a correct numerical setup for calculating the final volume of the helium gas
sample.
18. Convert the final temperature of the helium gas sample to degrees Celsius.
19. Base your answer to the following question on the information below.
The compounds NH4Br(s) and NH 3(g) are soluble in water. Solubility data for NH4Br(s) in water are
listed in the table below.
Determine the total mass of NH4Br(s) that must be dissolved in 200. grams of H2O at 60.°C to produce a
saturated solution.
20. Base your answer to the following question on the information below.
Air bags are an important safety feature in modern automobiles. An air bag is inflated in
milliseconds by the explosive decomposition of NaN3(s). The decomposition reaction produces N2(g),
as well as Na(s), according to the unbalanced equation below.
NaN3(s) ®Na(s) + N2(g)
Balance the equation for the decomposition of NaN 3, using the smallest whole-number coefficients.
21. Base your answer to the following question on
the information below.
Ammonium chloride is dissolved in water to form a 0.10 M NH4Cl(aq) solution. This dissolving process
is represented by the equation below.
State evidence that indicates the dissolving of ammonium chloride is an endothermic process.
Base your answers to questions 22 and 23 on on the
information below.
A 100.0-gram sample of NaCl(s) has an initial
temperature of 0°C. A chemist measures the
temperature of the sample as it is heated. Heat is not
added at a constant rate. The heating curve for the
sample is shown below.
22. Identify one line segment on the curve where the NaCl
sample is in a single phase and capable of conducting
electricity.
23. Identify one line segment on the curve where the
average kinetic energy of the particles of the NaCl
sample is changing.
24. Base your answer to the following question on the
information below.
A lightbulb contains argon gas at a temperature
of
and at a pressure of kilopascals. The
lightbulb is switched on, and after minutes its
temperature is
.
Show a correct numerical setup for calculating the
pressure of the gas inside the lightbulb at
.
Assume the volume of the lightbulb remains constant.
Base your answers to questions 25 and 26 on the information below.
During a fireworks display, salts are heated to very high temperatures. Ions in the salts
absorb energy and become excited. Spectacular colors are produced as energy is emitted from
the ions in the form of light.
The color of the emitted light is characteristic of the metal ion in each salt. For
example, the lithium ion in lithium carbonate, Li2CO3, produces a deep-red color. The
strontium ion in strontium carbonate, SrCO3, produces a bright-red color. Similarly, calcium
chloride is used for orange light, sodium chloride for yellow light, and barium chloride for
green light.
25. Explain, in terms of subatomic particles and energy states, how the colors in a fireworks display are
produced.
26. Write the formula for the salt used to produce green light in a fireworks display.
Base your answers to questions 27 through 29 on the
information below.
In 1864, the Solvay process was developed to make
soda ash. One step in the process is represented by the
balanced equation below.
NaCl + NH3 + CO 2 + H2O ®
NaHCO 3 + NH 4Cl
27. In the space draw a Lewis electron-dot diagram for the
reactant containing nitrogen in the equation.
28. Explain, in terms of electronegativity difference, why
the bond between hydrogen and oxygen in a water
molecule is more polar than the bond between
hydrogen and nitrogen in an ammonia molecule.
29. Write the chemical formula for one compound in the
equation that contains both ionic bonds and covalent
bonds.
30. Determine the mass of 5.20 moles of C 6H12 (gram-formula mass = 84.2 grams/mole)
Base your answers to questions 31 and 32 on the
information and diagram below.
One model of the atom states that atoms are tiny
particles composed of a uniform mixture of positive and
negative charges. Scientists conducted an experiment
where alpha particles were aimed at a thin layer of gold
atoms.
Most of the alpha particles passed directly through
the gold atoms. A few alpha particles were deflected
from their straight-line paths. An illustration of the
experiment is shown below.
31. A few of the alpha particles were deflected. What does
this evidence suggest about the structure of the gold
atoms?
32. Most of the alpha particles passed directly through the
gold atoms undisturbed. What does this evidence
suggest about the structure of the gold atoms?
33. Base your answer to the following question on
the data table below, which shows three isotopes of neon.
Based on the atomic masses and the natural abundances shown in the data table show a correct numerical
setup for calculating the average atomic mass of neon.
34. In a laboratory experiment, a student determined the mass of the product, NaNO 3(s), to be 0.105 grams.
a. Calculate the gram formula mass of NaNO 3(s). Round atomic masses from the Periodic Table to the
nearest tenth. [ Show all work. Indicate the correct answer in proper significant figures and include an
appropriate unit.]
b. Calculate the number of moles of NaNO 3(s) produced. [Show all work. Indicate the correct answer in
proper significant figures.]
Base your answers to questions 35 and 36 on the information below and on your knowledge of chemistry.
There are six elements in Group 14 on the Periodic Table. One of these elements has the symbol
Uuq, which is a temporary, systematic symbol. This element is now known as flerovium.
35. Identify an element in Group 14 that is classified as a metalloid.
36. State the expected number of valence electrons in an atom of the element flerovium in the ground state.
37. Base your answer to the following question on
the information below.
The atomic number and corresponding atomic radius of the Period 3 elements are shown in the data
table below.
Explain, in terms of electrons, the change in radius when a sodium atom becomes a sodium ion.
38. Base your answer to the following question on the information below and on your knowledge of chemistry.
Silver-plated utensils were popular before stainless steel became widely used to make eating utensils.
Silver tarnishes when it comes in contact with hydrogen sulfide,
, which is found in the air and in
some foods. However, stainless steel does not tarnish when it comes in contact with hydrogen sulfide.
In the ground state, an atom of which noble gas has the same electron configuration as the sulflde ion in
?
39. The table below shows the data collected during the heating of a 10.0-gram sample of a hydrated salt.
a What is the percent by mass of water in the original sample?
b Why is it important in this experiment to heat the salt until the mass of salt remains constant?
40. Base your answer to the following question on
the information below and on your knowledge of chemistry.
Seawater contains dissolved salts in the form of ions. Some of the ions found in seawater are
An investigation was conducted to determine the concentration of dissolved salts in seawater at
one location. A 300.-gram sample of the seawater was placed in an open container. After a week, all
the water had evaporated and 10. grams of solid salts remained in the container.
At standard pressure, compare the freezing point of seawater to the freezing point of distilled water.