A 25 mL class A pipet and an Ohaus Explorer model EX124 analytical balance are used to obtain the following experimental data:Trial 1 (g)Trial 2 (g)Trial 3 (g)Trial 4 (g)Trial 5 (g)Mass Beaker54.600354.599654.600354.598754.5995Mass w solution80.218080.114180.018780.650480.7774Solution NumberMass NaCl (g)Volumetric Flask (mL)Pipet (mL)Mass BeakerMass Beaker w solution11.05471002568.4012156993.5627530521.98651002568.4006758193.740100333.00581002568.4011903993.9284989444.09871002568.4002353294.1344957354.99841002568.401387494.298831566.02451002568.4009346294.50244286

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Chemistry 366 Homework Problem Set

Widener University

Dr. Van Bramer

January 2019

Propagation of Error and Statistics Worksheet

A 25 mL class A pipet and an Ohaus Explorer model EX124 analytical balance are used to obtain the

following experimental data:

Mass Beaker

Mass w

solution

1.

2.

3.

4.

5.

6.

Trial 1 (g)

54.6003

80.2180

Trial 2 (g)

54.5996

80.1141

Trial 3 (g)

54.6003

80.0187

Trial 4 (g)

54.5987

80.6504

Trial 5 (g)

54.5995

80.7774

Calculate the density of the solution for each trial

Use propagation of error to determine the uncertainty in the density of the solution for each trial.

Determine the average density for the solution.

Determine the standard deviation for the density of the solution.

Determine the 90% confidence interval for the density of the solution.

Determine the 95% confidence interval for the density of the solution.

A set of salt water standards is created by weighing sodium chloride, adding to a 100 mL class A volumetric

flask and diluting to the mark. 25 mL of this solution is transferred into a beaker with a class A volumetric

pipet.

Solution

Number

1

2

3

4

5

6

1.

2.

3.

4.

Mass NaCl (g)

1.0547

1.9865

3.0058

4.0987

4.9984

6.0245

Volumetric Flask

(mL)

100

100

100

100

100

100

Pipet (mL)

Mass Beaker

25

25

25

25

25

25

68.40121569

68.40067581

68.40119039

68.40023532

68.4013874

68.40093462

Mass Beaker w

solution

93.56275305

93.7401003

93.92849894

94.13449573

94.2988315

94.50244286

Create a calibration curve using the density and salinity (ppt) of the standards.

Use this calibration curve to determine the salinity of the unknown solution for each trial

Determine the average salinity for the solution

Determine the uncertainty in the salinity of the solution based on the uncertainty in the calibration

curve.

5. Determine the standard deviation for the salinity of the solution

6. Determine the 90% confidence interval for the salinity of the solution

7. Determine the 95% confidence interval for the salinity of the solution

trial 1

trial 2

trial 3

trial 4

trial 5

average

mass beaker mass w solution solution mass

54.6003

80.2180

25.6177

54.5996

80.1141

25.5145

54.6003

80.0187

25.4184

54.5987

80.6504

26.0517

54.5995

80.7774

26.1779

54.5997

80.3557

25.7560

std. dev.

90% interval

95% interval

0.3380

density

1.0247

1.0206

1.0167

1.0421

1.0471

1.0302

volume

25.0000

25.0000

25.0000

25.0000

25.0000

25.0000

% uncertainty

80.9000

80.8000

80.7000

mass with solution (g)

uncertainty

80.6000

80.5000

80.4000

80.3000

80.2000

80.1000

80.0000

79.9000

54.5986

54.5988

54.5990

54.5992

54.5994

mass beaker (g)

y = -361.82x + 19836

54.5994

54.5996

mass beaker (g)

54.5998

54.6000

54.6002

54.6004

solution no. NaCl (g)

Flask (ml)

pipet (ml)

mass beaker beaker w solution

1

1.0547

100

25 68.4012157

93.5627531

2

1.9865

100

25 68.4006758

93.7401003

3

3.0058

100

25 68.4011904

93.9284989

4

4.0987

100

25 68.4002353

94.1344957

5

4.9984

100

25 68.4013874

94.2988315

6

6.0245

100

25 68.4009346

94.5024429

…

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