Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition

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Experiment 1
This may be a student’s first experience in the laboratory. Therefore, the instructor should
demonstrate all the techniques used in this laboratory. Show how a Bunsen burner is lit, with a
match or a gas striker, and how the flame is adjusted by control of the gas valve and air vents.
This is a relatively simple laboratory for students to work. Most of the common
equipment used in the laboratory are introduced here. For many this might be the first time some
of the glassware will be encountered. For the instructor, patience is in order since the lack of
familiarity of the student with the laboratory ware often creates problems. Take the graduated
cylinder, for example. Since it is tall, it is easily knocked over, and although laboratory
glassware is reasonably durable, it will shatter and could cause severe cuts. Remind students not
to pick up broken glass with the fingers but to use the dustpan and brush. Broken glass should be
discarded in a waste container specifically for glass.
While there is little danger in this laboratory of eye damage, nevertheless, it is essential
that the rules of the laboratory be followed: safety glasses are to be worn at all times in the
laboratory.
The thermometers in this laboratory are made of glass and must be handled properly. A
thermometer is not a stirring rod and must not be used as such. If a student wants to bring the
fluid level in the thermometer down, remind him/her to use cold water from the tap. The
laboratory thermometer is not a clinical thermometer and does not require that it be shaken
down! Waving the thermometer usually results in it hitting a bench top and breaking. Some of
these thermometers contain mercury; the breakage of a thermometer with resultant spillage of
mercury must be cleaned up quickly. Mercury is toxic, especially as a vapor. The instructor
should be notified immediately for proper clean up. No mercury should be left freely about
anywhere. Mercury can be collected with commercial collectors or by a homemade suction
apparatus. Connect a side-arm suction filter flask to a water aspirator. The flask is fitted with a
one-hole rubber stopper with a small section of glass tubing inserted into the hole. Rubber tubing
connects the glass tube to a Pasteur pipet. When the water is turned on, the spheres of mercury
will be sucked into the pipet and then into the suction flask. The recovered mercury can be stored
under water.
Balances should be handled with care; electronic top-loading balances are sensitive and
lose calibration easily. Demonstrate proper use of the balance. Emphasize that no chemical
should be weighed directly on the pan; use either weighing paper or a suitable container. Also
hot objects should not be put on the pan. Proper care requires that all weights be returned to zero.
The difference between precision and accuracy can be easily demonstrated. Use two
balances, one that has been zeroed and calibrated, a second not zeroed and uncalibrated.
Repeated weighings of the same object of known weight on the two balances will show high
precision (high reproducibility in the clustering of the weights) for each of the two balances but
not the same accuracy (agreement with the known weight).

name section date
partner grade
1 E X P E R I M E N T 1
Pre-Lab Questions
1. In the design of a Bunsen burner, explain the purpose of
a. the gas control valve
Manipulation of this valve controls the flow of gas
b. and the air vents.
Manipulation of these vents controls the mixing of air with gas; allows the control of flame temperature.
2. Why is a luminous yellow flame often ‘‘smoky’’?
Lack of sufficient air causes incomplete burning of the gas and produces soot.
3. A student wanted 20.000 g of a salt. Which balance should the student use in order to obtain the most
accurate quantity: a platform triple beam balance, a single pan, triple beam balance, or a top-loading balance?
Explain your answer.
The top-loading balance enables you to weigh to the nearest 0.001 g.
4. Explain the difference between precision and accuracy?
Precision determines the reproducibility of a measurement; accuracy is a measure of how closely the value determined
agrees with a known or accepted value.
5. Solve the following problems and record the answers to the proper number of significant figures.
a. 21.65 - 3.2= 18.5
b. 4.01 ÷ (4.583 + 2.108)= 0.599
c. 6.15 ÷ 1.2 = 5.1
d. 2.26 x 21.43= 48.4
2

name section date
partner grade
1 E X P E R I M E N T 1
Report Sheet
Bunsen burner
1. What is the color of the flame when the air vents are closed?
Yellow
2. Did anything happen to the surface of the Pyrex test tube in this flame?
Soot collected on the test tube
3. What happens to the flame size when the gas control valve is turned?
The flame changes in size
4. Describe the effect on the flame as the air vents were opened.
The flame looses the yellow color and becomes blue
Length
1. Length 27.5 cm
Width 21.5 cm
2. Length 275 mm 0.275 m
Width 215 mm 0.215 m
3. Area 591 cm2
(Show calculations)
27.5 x 21.5= 591.25= 591
275 x 215= 59125= 59100
59100 m
3

Volume
1. Erlenmeyer flask 49.5 mL 0.0495 L
2. Beaker 42.0 mL 0.0420 L
3. Error in volume:
Erlenmeyer flask 0.5 mL 1% %
Beaker 2.0 mL 5.0% %
Error in volume
Total volume
% Error = x100 (Show your calculations)
(0.5/50) x 100=1% (2.0/40) x 100= 5.0%
4. Graduated cylinder
Mass
Object
Balance
Platform Single Pan, Triple Beam Top Loading
g mg g mg g mg
Quarter 5.8 5800 5.61 5610 5.613 5613
Test tube (100 13 mm) 8.1 8100 7.92 7920 7.872 7872
125-mL
Erlenmeyer flask
77.1 77100 76.95 76950 76.948 76948
Temperature
8C 8F K
Room temperature 22.5 72.5 295.7
Ice water 0.5 32.9 273.7
Boiling water 99.5 211.1 372.7
How well do your thermometer readings agree with the accepted values for the freezing point and
boiling point of water? Express any discrepancy as a deviation in degrees.
Freezing Point: + 0.5 degrees Celsius Boiling Point: -0.5 degrees Celsius
4

Post-Lab Questions
1. How does a student need to adjust the Bunsen burner in order to change a luminous yellow
flame into a nonluminous blue flame?
Open the air vents at the bottom of the burner barrel; more air assures complete combustion.
2. What causes the luminescence in the cooler, yellow flame?
Unburned small particles of carbon, soot, causes the luminescence.
3. A student needed exactly 45.3 mL of a solution. What piece of glassware should that student use?
Justify your choice.
The graduated cylinder has gradations in 0.1 mL and would give the more accurate measure.
3. The diagram below is of a nonluminous Bunsen flame. Indicate the approximate region of the
hottest part of the flame.
The tip of the inner blue cone is the hottest part of the flame.
5. Two students weighed a 125-mL beaker that had a mass of 80.562 g on a calibrated top-loading
balance. Each student used their own top-loading balance, recorded three mass readings for the
beaker, and then determined the average. Below are the results:
Student A Student B
80.560 80.400
80.555 79.551
80.565 81.729
Average: 80.560 80.560
a. Find the averages.
b. Which set of results matches the known mass of the beaker?
Both sets agree well with the known weight of the beaker.
c. Which set of results is more precise?
Student A has a balance that gives more precise results; the weights are more reproducible
d. Which student has the more reliable balance?
Student A has a more reliable balance
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6. A student measured the dimensions of a table and recorded the length as 103.50 cm and the
width as 73.75 cm. According to the student’s calculator, the area is 7633.125 cm2. What should the
student report? Explain your answer.
The answer is good to only 4 significant figures. The answer is 7633 cm square.
7. John has a mass of 115 kg. Sally has a mass of 115 lb. Who is the heavier of the two? Show
your calculations to justify your answer.
115 kg x 2.20 lb/kg=253lb. John is heavier
8. At 20,320 ft., Mount McKinley in Alaska is the highest peak in North America. Express the
height in meters (m) and kilometers (km) to the correct number of significant figures. Show your
work.
20,320 ft x 30.48 cm/ft x 1 m/100 cm x 1 km/100m = 6.194 km
20,320 ft x 30.48 cm/ft x 1 m/100 cm = 6194 m
9. A 16.95 g sample of sugar was added to a glass with a mass of 8.3 oz. What is the combined
mass of the glass and the sample in ounces (oz.), grams (g), and milligrams (mg)? Show your
work and express your answers to the correct number of significant figures.
8.3 oz. x 28.35 g/oz. = 235.3 g or 240 g to 2 sig. fig.
16.95 g + 235.3 g= 252.3 g or 16.95g +240 g= 257 g if you follow sig. fig. rules
257 g x 1000 mg/g= 257,000 mg
16.95 g x 1 oz./28.35g= 0.5979 oz.
8.3 oz. + 0.5979 oz. = 8.8979 oz. = 8.9 oz. to 2 sig. fig.
6

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Experiment 2
This laboratory provides a bit of fun for the student; the student will use the experiment
in the locker to solve a puzzle. Each will be given unknowns of various kinds and asked to find
out the identities by taking suitable measurements. Thus, using precision, accuracy, and
significant figures in their measurements, each unknown can be identified. (Eureka!)
In the use of balances, again remind students not to weigh directly on the pan, but to use a
container or weighing paper. In the case of the unknown metal, provide suitable containers for
their recovery. For the other unknowns, waste containers should be provided. Nothing should be
discarded into the sink.
Reading the volume in a graduated cylinder requires lining up of the eye with the
meniscus. Demonstrate the proper technique for doing this. It may be the student’s first
encounter with the Spectroline pipet filler. It would be best to go through the way it works,
particularly in the suction phase of its use. If the tip of the pipet is not immersed far enough into
the liquid to be pipetted, the force of the suction might cause the liquid to be drawn up into the
Spectroline pipet filler’s body; these liquids will cause the inside to deteriorate. In addition, the
liquids in the pipet filler will contaminate the next liquid to be pipetted, and so this situation
should be avoided.

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name section date
partner grade
2 E X P E R I M E N T 2
Pre-Lab Questions
1. How does an intensive property differ from an extensive property? Give an example of an
intensive property and of an extensive property.
The intensive property does not depend on the quantity of the substance: density.
An extensive properly depends on the quantity of the substance: mass.
2. In order to calculate the density of a solid or liquid sample, what measurements are needed?
You need a mass measurement and a volume measurement.
3. The volume of a fixed mass of a liquid sample increases as the temperature rises from 20 to
40 8 C. Does the density increase, decrease, or stay the same? Explain your answer.
As the temperature rises, there is a change in the volume, the volume gets larger. As a result,
the density will decrease. (mass/volume= density) Remember, there is no change in the mass;
the only factor changing is the volume (you are dividing by a bigger number as the volume
increases with increasing temperature).
4.A solid block of exactly 100.0 cm3 has a mass of 153.6 g. Determine its density. Will the block sink or
float on water?
153.6g/100.0 cc = 1.53 g/cc. This density is greater than the density of water, so it will sink.
5. A salvage operator recovered coins believed to be gold. A sample had a mass of 129.6 g and
had a volume of 15.3 cm3. Were the coins gold (d = 19.3 g/cm3) or just yellow brass (d = 8.47
g/cm3)? Show your work.
129.6 g/15.3 cc = 8.47 g/cc Too bad, the metal is brass.
8

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name section date
partner grade
2 E X P E R I M E N T 2
Report Sheet
Report all measurements and calculations to the correct number of significant figures.
Density of a regular-shaped object Trial 1 Trial 2
Unknown code number 1 (wood block)
1. Length 20.8 cm 20.8 cm
Width 5.3 cm 5.3 cm
Height
2. Volume (L W H)
3. Mass
4. Density: (3)/(2)
Average density of block
4.4 cm
485 cm3
287.57 g
0.593 g/cm3
4.4 cm
485 cm3
287.62 g
0.593 g/cm3
0.593 g/cm3
Density of an irregular-shaped object Trial 1 Trial 2
Unknown code number 2 (Al shot)
5. Mass of metal sample 5.232 g 6.702 g
6. Initial volume of water 14.90 mL 16.80 mL
7. Final volume of water
8. Volume of metal: (7) (6)
9. Density of metal: (5)/(8)
16.80 mL
1.90 mL
2.75 g/mL
19.30 mL
2.50 mL
2.68 g/mL
Average density of metal 2.72 g/mL
10. Identity of unknown metal Aluminum
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Density of water Trial 1 Trial 2
11. Temperature of water 22.0 8 C 22.0 8 C
12. Mass of 50-mL beaker 26.264 g 26.257 g
Volume of water 10.00 mL 10.00 mL
13. Mass of beaker and water
14. Mass of water: (13) (12)
15. Density of water: (14)/10.00 mL
36.143 g
9.879 g
0.9879 g/mL
36.176 g
9.919 g
0.9919 g/mL
16. Average density of water 0.998 g/mL
Density found in literature 0.998 g/mL
Density of an unknown liquid Trial 1 Trial 2
Unknown code number 3 (ethyl alcohol)
17. Temperature of unknown liquid 22.0 8 C 22.0 8 C
18. Mass of 50-mL beaker 26.810 g 26.960 g
Volume of liquid 10.00 mL 10.00 mL
19. Mass of beaker and liquid
20. Mass of liquid: (19) (18)
21. Density of liquid: (20)/10.00 mL
34.671 g
7.861 g
0.7861 g/mL
34.842 g
7.882 g
0.7882 g/mL
Average density of unknown liquid 0.7872 g/mL
22. Identity of unknown liquid Ethyl alcohol
10

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Post-Lab Questions
1. In determining the density of olive oil (see Table 2.2), one student took exactly 25.00 mL and
found the mass to be 22.95 g. A second student took exactly 50.00 mL and found the mass to be
45.90 g. Will each student arrive at the same value for the density? Do each calculation and
explain the result.
22.95 g/25.00 mL = 0.918 g/mL 45.90 g/50.00 mL = 0.918 g.mL
Each student will arrive at the same value for the density because density is an intrinsic
property; the ratio of mass to volume is the same.
2 . Hexane has a density of 0.659 g/mL. How many milliliters (mL) would a student need to pour
in order to get 49.5 g of hexane? Show your work.
If density = mass/volume then volume = mass/density or mL = g/g/mL = g x mL/g
49.5 g/0.659 g/mL = 75.1 mL
3. In the density determination of a liquid, it was necessary to use the volumetric pipet properly.
A student needed to deliver exactly 50.0 mL of a liquid. How will the quantity of liquid be affected
by the situations described below, and how will the density determination be affected?
a. A dirty pipet is used and droplets of liquid adhered to the inner walls of the pipet.
Density determined decreases. The measured mass of the liquid delivered would be less than it should be
(droplets remain in the piper), but the volume is still assumed to be 50.0 mL.
b. The student did not allow sufficient time for all the liquid to empty from the pipet.
Density determined decreases. The mass measured would be less (not everything has been
transferred) but the volume is still assumed to be 50.0 mL.
c. The student allowed all the liquid to drain and then blew out the small amount from the tip.
Density determined increases. The mass measured would be greater since more liquid has been
delivered than allowed for by calibration, but the volume is still assumed to be 50.0 mL.
d. Air bubbles were not removed from the pipet before delivering the liquid.
Density determined decreases. The mass measure would be less (air took up space of the liquid),
but the volume is still assumed to be 50.0 mL
e. At the mark on the pipet, the student read the upper edge of the meniscus and not the
lowest point on the curve.
Density determined decreases. The mass measured would be less since less than 50.0 mL would
be delivered, but the volume is still assumed to be 50.0 mL.
11

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Experiment 3
In this experiment students get to use a Bunsen burner to heat various mixtures. Remind
students by means of a demonstration the workings of a Bunsen burner. The instructor should
check to make sure that the ring clamp is secured tightly to the ring stand and set at the proper
height above the flame. All heating should be done with a wire gauze under the beaker.
A major source of error occurs in the gravity filtration of the stand. Remind the students
to be careful and patient in the transfer. With the rubber policeman as an aid, all the sand can be
transferred from the filter paper to the second beaker. Again care and patience will result in all of
the sand being transferred.
The evaporation of water needs to be carefully done. As the salt-water solution reaches
dryness, the residual salt will spatter; the student must be prepared to pull away the Bunsen
burner to reduce the heat when this occurs in order to minimize losses from solid flying out of
the beaker. This also applies to drying of the sand; as the water evaporates from the sand, trapped
vapor will cause spattering.
Both the salt and the sand must be water free in order for the calculations to be
meaningful. The dry salt will appear as a cake; the dry sand should be freely flowing when
poured.
Provide a waste container to collect the used naphthalene. Sand and dried salt can be
disposed in solid waste containers.

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name section date
partner grade
3 E X P E R I M E N T 3
Pre-Lab Questions
1. I make my cup of coffee in the morning by pouring boiling water over ground-up coffee beans held
in a special piece of paper and by collecting the brown liquid that comes through. Which techniques
of the five described in the Background section is used in the preparation of the drink?
Extraction is used.
2. I like my coffee sweet, so I add a tablespoon of sugar to my cup of coffee and the solid disappears.
What makes up the ‘‘cup of coffee’’ now? Is this a mixture?
It is a mixture of dissolved sugar and extracted substances from the coffee bean.
3. What is taking place during the process of sublimation? How is this process different from
evaporation?
Sublimination is a process that involves heating a solid until its molecules pass directly from the
solid phase into the gaseous phase. Evaporation involves molecules in the liquid phase escaping
into the gaseous phase.
4 . Are any of the techniques described in the Background section a chemical state change?
Explain your answer.
No chemical state changes are involved, only physical state changes. This is because no chemical
bonds have been broken.
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name section date
partner grade
3 E X P E R I M E N T 3
Report Sheet
1. Mass of beaker 1 67.565 g
2. Mass of beaker 1 and mixture 68.730 g
3. Mass of mixture: (2) (1) 1.165 g
4. Mass of naphthalene collected 0.095 g
5. a. Mass of beaker 1 and solid after sublimation 68.616 g
b. Mass of naphthalene by difference: (2) (5a) 0.114 g
6. Mass of beaker 2 67.959 g
7. Mass of beaker 2 and NaCl 68.530 g
8. Mass of NaCl: (7) (6) 0.571 g
9. Mass of beaker 3 55.765 g
10. Mass of beaker 3 and sand 56.231 g
11. Mass of sand: (10) (9) 0.466 g
Calculations
12. Mass of recovered solids:
(5b) + (8) + (11) 1.151 g
13. Percentage yield (percentage of solids recovered):
% ¼ [(12)/(3)] 100 98.80 %
14. Percentage of naphthalene:
% ¼ [(5b)/(3)] 100 9.79 %
15. Percentage of NaCl:
% ¼ [(8)/(3)] 100 49.01 %
16. Percentage of sand:
% ¼ [(11)/(3)] 100 40.00 %
14

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Post-Lab Questions
1. A student completed the experiment but found that the total amount of material recovered
weighed more than the original sample. What is the most likely source of error and
how may it be corrected?
Most likely water is present. Heat to evaporate the water
2. A student found that the mass of the naphthalene collected was less than the mass
determined by difference. What would account for the smaller amount of
naphthalene collected?
If naphthalene vapors escaped, then not all of the naphthalene was collected.
3.Mothballs in a clothes closet gradually disappear over time. What happens to this material?
The solid mothballs sublimed.
4. A package of freshly picked sweet peas has a mass of 454 g (1 lb.). The peas were freeze
dried and the recovered peas weighed 122 g. What was lost? What is the percent
composition of this volatile component?
(454 – 122) /454 x 100 = 73.1 %
5. In 100 g of sweet peas, there are 14.5 g carbohydrates, 5.7 g sugars, 5.1 g dietary fiber,
5.4 g protein, and 0.4 g fat. Calculate the percent composition for each of these components.
14.5/100 x 100 = 14.5% carbohydrates 5.1/100 x 100= 5.1% dietary fiber
5.7/100 x 100 = 5.7% sugars 5.4/100 x 100= 5.4% protein
0.4/100 x 100 = 0.4% fat
15

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Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition

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