Experiment a5 evidence for chemical change

Two Lab Reports
Final Report

Exercise 1

CHEM 181 DL1 Laboratory Techniques and Measurements

The reason could be atmospheric pressure changes with the higher sea levels, decreasing the degree at which it takes water to boil.

1. Water boils at 100°C at sea level. If the water in this experiment did not boil at 100°C, what could be the reason?

100(102-100)/100=2% error

100(99.2-100)/100=-0.8% error

2. While heating two dif f erent samples of water at sea level, one boils at 102°C and one boils at 99.2°C. Calculate the percent error f or each sample f rom the theoretical 100.0°C.

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Data Table 1: Length Measurements

Data Table 2: Temperature Measurements

Length (cm)

CD or DVD

Key

Spoon

Fork

Length (mm)

CD or DVD

Key

Spoon

Fork

Length (m)

CD or DVD

Key

Spoon

Fork

12

5.5

18

18

120

55

180

180

0.12

0.055

0.18

0.18

Temperature (°C)

Hot from Tap

Boiling

35

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Boiling for 5 minutes

Cold from Tap

Ice Water - 1 minute

Ice Water - 5 minutes

Temperature (°F)

Hot from Tap

Boiling

Boiling for 5 minutes

Cold from Tap

Ice Water - 1 minute

Ice Water - 5 minutes

Temperature (K)

Hot from Tap

Boiling

Boiling for 5 minutes

Cold from Tap

Ice Water - 1 minute

Ice Water - 5 minutes

85

100

20

2

-1

95

185

212

68

35.6

30.2

308.15

358.15

373.15

293.15

275.15

271.15

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Data Table 3: Mass Measurements

Estimated Mass (g)

Pen or Pencil

3 Pennies

1 Quarter

2 Quarters, 3 Dimes

4 Dimes, 5 Pennies

3 Quarters, 1 Dime, 5 Pennies

Key

Key, 1 Quarter, 4 Pennies

Actual Mass (g)

Pen or Pencil

3 Pennies

1 Quarter

2 Quarters, 3 Dimes

4 Dimes, 5 Pennies

3 Quarters, 1 Dime, 5 Pennies

Key

Key, 1 Quarter, 4 Pennies

Actual Mass (kg)

Pen or Pencil

4

8

4

12

21

30

7

18

5.6

7.5

5.6

18

22.1

32.3

7.7

24

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Exercise 2

3 Pennies

1 Quarter

2 Quarters, 3 Dimes

4 Dimes, 5 Pennies

3 Quarters, 1 Dime, 5 Pennies

Key

Key, 1 Quarter, 4 Pennies

0.0056

0.0075

0.0056

0.018

0.0221

0.0323

0.0077

0.024

Density= mass/ volume

Volume= length x width x height

Volume= 3.6 x 4.21 x 1.17= 17.73 cm

Density= 21.3/17.73= 1.20 g/mL

1. An unknown, rectangular substance measures 3.60 cm high, 4.21 cm long, and 1.17 cm wide. If the mass is 21.3 g, what is this substance’s density (in grams per milliliter)?

3

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Density= mass/volume

Volume= mass/ density

Volume= 26.15/19.30= 1.35 mL Au

2. A sample of gold (Au) has a mass of 26.15 g. Given that the theoretical density is 19.30 g/mL, what is the volume of the gold sample?

If you dropped the object into the beaker then the scale would measure the mass of the object instead of the mass of the displaced water and the measurements would be thrown off.

3. What would happen if you dropped the object into the beaker while using the Archimedes’ Principle method instead of submerging the object?

How the magnets density measurement using the Archimedes principles compare to the density measurement using the calculated volume is that the magnets density measurement during the Archimedes was higher than the density measurement using the calculated volume. I think that the Archimedes principle method might be more accurate because with the calculated volume there is more room for error as I made the measurements.

4. How did the magnet’s density cdalculation using the Archimedes’ Principle compare to the density calculation using the direct measurement method? Which technique might be more accurate? Why?

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Data Table 4: Liquid Measurements

The conclusions I can reach from the simple density analysis is that is could not actually be gold because pure gold is 19.32 g/cm .

5. You are given a small piece of gold colored material and want to determine if it is actually gold. Using the Archimedes Principle you f ind that the volume is 0.40 cm and the mass is 6.0 g. What conclusions can you reach f rom your simple density analysis?

3

3

Water

Mass A: Graduated Cylinder (g)

Volume (mL)

Mass B: Graduated Cylinder with Liquid (g)

Mass B-A: Liquid (g)

Density (g/mL)

Percent Error (%)

Isopropyl Alcohol

Mass A: Graduated Cylinder (g)

Volume (mL)

Mass B: Graduated Cylinder with Liquid (g)

Mass B-A: Liquid (g)

Density (g/mL)

Percent Error (%)

19.3

5

24.4

5.1

1.00

26.4%

19.3

5

23.6

4.3

0.786

22.3%

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Data Table 5: Magnet - Direct Measurement Method

Data Table 6: Water Displacement Method

Magnet

Mass (g)

Length (cm)

Width (cm)

Height (cm)

Volume (cm )

Density (g/cm )

4.2

2.5

0.5

2.5

3 3.125

3 1.344

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Data Table 7: Archimedes' Method

Magnet

Mass (g)

Initial Volume of Graduated Cylinder (mL)

Final Volume of Graduated Cylinder (mL)

Object Volume (mL)

Density (g/mL)

Metal Bolt

Mass (g)

Initial Volume of Graduated Cylinder (mL)

Final Volume of Graduated Cylinder (mL)

Object Volume (mL)

Density (g/mL)

4.3

6

6.5

0.5

8.6

8

6

7

1

8

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Exercise 3

Magnet

Mass (g)

Mass of Displaced Water (g)

Volume of Displaced Water (mL)

Density (g/mL)

Metal Bolt

Mass (g)

Mass of Displaced Water (g)

Volume of Displaced Water (mL)

Density (g/mL)

4.3

121.4

121.4

1

8

121.8

121.8

1

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Data Table 8: Initial Concentration

1% x V1 = 2% x 2V

0.25 x 10 = 1 x 2V

V2= 0.25 x10/1

V2= 2.5mL

How I would prepare 10 mL of a 0.25% HCl solution if 1% HCl available is dilute the 1% in water to get a less concentrated .25% HCl. Then determine the amount of moles by multiplying 0.01 and .25 which equals 0.0025 moles HCl. Then, you prepare 10 mL containing 2.5 mL of 1% HCl.

1. How would you prepare 10 mL of a 0.25% m/v HCl solution if 1% m/v HCl was available? How much 1% m/v HCl is needed? How much distilled water is used?

The relations between the concentration of the sugar solution and the density of the sugar solution is that the density is a lot higher than the comcentration.

2. From the graph of Density vs. Concentration, created in Graph 1, what was the relationship between the concentration of the sugar solution and the density of the sugar solution?

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Data Table 9: Solutions

Sugar (C H O )

Mass of Volumetric Flask (g)

Mass of Sugar (g)

Total Volume (mL)

Concentration (% m/V)

12 22 11

19.3

8

0.025

0.92%

Solution Volume (mL)

0 25.00 mL

1 25.00 mL

2 25.00 mL

3 25.00 mL

4 25.00 mL

Solution Mass (g)

0

1

2

3

4

Solution Density (g/mL)

0

1

26.5

25.3

25.4

25.4

25.5

1.06

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2

3

4

Solution Initial Concentration (% m/v)

0

1

2

3

4

Solution Volume Transferred (mL)

0

1

2

3

4

Solution Final Concentration (% m/v)

0

1

2

3

1.012

1.016

1.016

1.02

0.92%

2.9%

2.9%

2.9%

0

2.5

4.5

3

6

0.925

2.9%

13.05%

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Graph 1: Density versus Concentration

4

8.7%

17.4%