UAB Data Collection of Water Series & Density of Dilutions Chemistry Lab Report I have introduction section for lab chemistry report, i will upload an exam
UAB Data Collection of Water Series & Density of Dilutions Chemistry Lab Report I have introduction section for lab chemistry report, i will upload an example report so you can know what to do.((The INTRODUCTION should be written based on the background information presented in Canvas.))i will upload the background and lab report example Example CH116/118 Lab Report: Physical Properties
Group Members: Arianna Lacen, Carolina Grace, Haley Fiorucci, Shiyen Sinclair
Introduction
Density is an intrinsic property of a substance relating its mass and volume. Density can be
found using d, density, is to m, mass, divided by v, volume or d=m/v. This equation can be
rearranged to give a linear equation which can be used to plot mass against volume to find
density, which would be the slope. In this experiment, the density of water was found by
measuring its mass on a balance and its volume using graduated cylinders and pipets and the
volume by difference method.
Experimental
Materials
The materials used for this experiment were a 10 mL Mohr pipet and blue bulb, a 100
mL graduated cylinder, 150 mL beakers, a 25 mL volumetric flask, plastic transfer pipets, a
balance, deionized water, a 20% sugar solution, and a solution of unknown density.
Exercise 1
The balance was tared before an empty 150 mL beaker was placed inside it. Once the
mass stopped changing, it was recorded to the correct decimal place. To the 100 mL graduated
cylinder, a random volume of deionized water was added. The initial volume was read at eye
level and recorded. Then, the water was poured into the previously weighed 150 mL beaker.
The final volume left in the graduated cylinder was read at eye level and recorded. The beaker
was then reweighed, and the mass of the liquid was calculated. With the mass and volume
delivered known, the density of the water was calculated. This was repeated two more times so
an average and standard deviation could be calculated for the density achieved with the
graduated cylinder. Table 1 below contains the information regarding the masses and volumes
obtained, along with the densities and average density plus the standard deviation for the
graduated pipet.
The same procedure was repeated with the pipet, in which a random volume of water
was drawn into the pipet using the bulb and delivered into the empty 150 mL beaker. Masses
and volumes obtained between the three trials, along with the calculated densities and the
average density with standard deviation for the pipet can be seen in Table 2.
Exercise 2
Before diluting, the 10 mL Mohr pipet was primed by rinsing it first with deionized water
and then with the 20% sugar solution. This was performed three times.
A series of three dilutions was performed. First, the empty 25 mL volumetric flask was
weighed (Table 4). Then, a random volume of the sugar solution was added to the volumetric
flask (Table 3). A plastic transfer pipet was then used to dilute the solution with deionized
water to the 25 mL mark. The flask with the dilution was reweighed (Table 4), and the
concentration (Table 3) and density (Table 4) of the solution was calculated. The values of the
calculated densities and concentrations for the three trials performed were used to create a
calibration curve (Figure 1).
Exercise 3
A dry, empty 25 mL volumetric flask was weighed on the balance (Table 4). Using the 10
mL Mohr pipet, a random volume (Table 3) of the provided unknown solution was added to the
empty volumetric flask (Table 3), diluted with deionized water, and reweighed (Table 4). The
density calculated for the unknown was recorded in Table 5. Using Figure 1, the molarity of the
unknown dilution was determined. From the diluted concentration, the original concentration
of the unknown was determined.
Results
Table 1. Density Data Collection of Water Using 100 mL Graduated Cylinder
Trial
Mass of
Empty
Beaker (g)
Mass of
Beaker +
Water
(g)
Mass
of
Water
(g)
Initial
Volume
of Water
(mL)
Final
Volume
of Water
(ml)
Volume
Delivered
(mL)
Density
of
Water
(g/mL)
1
55.156
110.878
55.722
90.1
33.1
57.0
0.978
2
55.149
110.860
55.711
89.8
34.1
55.7
1.00
3
55.152
110.877
55.725
78.3
20.7
57.6
0.967
Average
Density
(g/mL)
Standard
Deviation
0.982
0.017
Table 1 denotes the data collected for the density of water using a 100-milliliter graduated
cylinder.
Table 2. Density Data Collection of Water Using 10 mL Mohr Pipet
Trial
Mass of
Empty
Beaker (g)
Mass of
Beaker
+ Water
(g)
Mass
of
Water
(g)
Initial
Volume
of Water
(mL)
Final
Volume
of Water
(ml)
Volume
Delivered
(mL)
Density
of
Water
(g/mL)
1
54.012
58.687
4.675
8.83
4.15
4.68
0.999
2
54.020
59.002
4.982
9.12
4.13
4.99
0.998
3
54.013
58.690
4.677
8.88
4.18
4.70
0.995
Average
Density
(g/mL)
Standard
Deviation
0.997
0.002
Table 2 denotes the data collected for the density of water using a 10-milliliter Mohr pipet.
Table 3. Series of Dilutions Using 20% Stock
Trial
Initial Molarity (%)
Initial Volume (mL)
Final Molarity (%)
Final Volume (mL)
1
20
5.45
4.4
25
2
20
6.78
5.4
25
3
20
7.99
6.4
25
Unknown
x
5.66
x
25
Table 3 denotes the data collected for the dilutions of a 20% stock sugar solution using the
dilution equation.
Table 4. Density of Dilutions
Trial
Mass of Empty 25-mL
Volumetric Flask
Mass of 25-mL Volumetric
Flask + 25 mL Soln
Mass of
Soln (g)
Volume
(mL)
Density
(g/mL)
1
22.347
48.809
26.462
25
1.055
2
22.349
49.577
27.228
25
1.089
3
22.350
50.001
27.651
25
1.106
Unknown
22.348
50.011
27.663
25
1.107
Table 4 denotes the data collected for the density of each dilution.
Density vs. Molarity of Dilutions (Trials 1-3)
1.12
y = 0.026x + 0.9433
R² = 0.9694
1.11
Density (g/mL)
1.1
1.09
Series1
1.08
Linear (Series1)
1.07
1.06
1.05
0
1
2
3
4
5
6
7
Molarity (%)
Figure 1. Density vs. Molarity of Dilutions in Trials 1-3.
Figure 1 exhibits the relationship between density and concentration.
Table 5. Density and Initial & Final Molarity of Unknown
Density (g/mL)
Final Molarity M2 (%)
Initial Molarity M1 (%)
1.107
6.296
7.870
Table 5 denotes the data collected of the Unknowns density and molarity values.
Discussion/Conclusions
The goal of this lab was to determine density using experimentally determined mass and
volume measurements. In exercise I, two different methods were used to deliver various
volumes of water into a pre-weighted beaker. The theoretical density of water is 1.00
g/ml. Thus, using the mohr pipet to deliver volume is more accurate than using the graduated
cylinder. In exercise II, we used sugar water to create a range of dilutions, and then determined
the density for each. Density was compared to relative concentration to establish the linear
relationship. The R-squared value is 0.9694. This means that the x and y axes (molarity and
density, respectively) of the calibration curve are correlated.
Properties that depend on the concentration of particles in solution are called colligative properties.
The number of particles in a solvent can affect the freezing or boiling point of solvent. To express the effect
of concentration on freezing point or boiling point, molality is used in place of molarity. Molality (m) is the
number of moles of solute per 1 kilogram of solvent.
moles of solute
molality (m) =
Kg of solvent
The presence of a solute affects the boiling point of a solvent by lowering the vapor pressure of that
solvent. The magnitude of this reduction in vapor pressure depends upon the concentration of solute
particles present in the solvent. Since the freezing point of a liquid depends on its vapor pressure,
introduction of a solute in a solvent will alter the boiling point of the solution from that of the pure solvent.
It is often necessary to determine the freezing point of a solvent or solution using cooling curves,
which are plots of time versus temperature. Generally, these plots show a steep decrease in temperature
over time, followed by a horizontal plateau. The point where these two lines meet corresponds to the
freezing point of the substance being measured. Figure 1 shows an example of a cooling curve.
Figure 1: Sample Cooling Curve for Benzophenone.
Cooling Curve
90
80
70
60
50
40
30
20
10
0
0 50 100 150 200
250
300
Time (s)
Temperature (degC)
Relevant equations related to freezing point depression
AT = T(solvent) – T (solution)
AT – Kr* m
where Te is freezing point (Recall that the freezing point is the same as the melting point.), Kç is the
freezing point constant for the solvent, and m is the molality of the solute.
The solvent used in the experiment is benzophenone. The expected freezing point (T (solvent))for
benzophenone is 48.1°C. Even though it is printed here, you should experimentally determine the freezing
point. The K for benzophenone is 9.80 °C/m.
You will be given an unknown solid. You will used the colligative property to calculate the molar
mass of this unknown. Example calculations are given in your textbook.
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