Strong Acid Base Report Sheets S2021-converted 2 PDF

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chemistry lab report sheet (strong acid-base)...

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STRONG ACID – STRONG BASE REPORT SHEET

Name:

Date:

Laboratory instructor: STANDARDIZATION OF 0.1 M NaOH SOLUTION TRIAL #1

TRIAL #2

TRIAL #3

1.

Weight of KHP used (in grams)

0.4820

0.4862

0.5040

2.

Final burette reading (in mL)

25.44

23.49

22.78

3.

Initial burette reading (in mL)

4.96

3.25

1.80

4.

mL of NaOH used (V)

20.48

20.24

20.98

5.

Moles of KHP (weight of KHP used) / 204.2

0.002360

0.002381

0.002468

6.

Moles of base

0.002360

0.002381

0.002468

7.

Molarity of the base (moles of base × 1000) / V

0.1152

0.1176

0.1176

8.

Average Molarity

0.1168

± 0.0011

9.

Average deviation in parts per thousand

9.4

M

Show your calculations for calculating the average deviation in an appendix: |0.1152 – 0.1168| = 0.0016 |0.1176 – 0.1168| = 0.0008

average deviation:

(0.0016+0.0008+ 0.0008) 3

|0.1176 – 0.1168| = 0.0008 Q1: What would be an appropriate method to statistically eliminate a trial should you feel that one trial is different from the others? Would this be practical with only three trials?

To reduce experimental error and to get a more accurate result, the titration should be performed a couple times each trial. This would be practical with only three trials as you are no eliminating a whole trial. But picking the best reading for each, therefore you would still have three trials instead of just two.

STRONG ACID – STRONG BASE REPORT SHEET

ANALYSIS OF UNKNOWN ACID: TRIAL #1

SAMPLE # 82 TRIAL #2

TRIAL #3

1.

Weight of unknown used (g)

0.5008

0.5180

0.5152

2.

Final burette reading (in mL)

11.42

11.10

20.80

3.

Initial burette reading (in mL)

2.68

1.28

11.10

4.

mL of NaOH used (V)

8.74

9.82

9.7

5.

Average molarity of NaOH (line 8, previous page)

0.1168

±

0.0011

±

0.1168

±

0.001 0.1168

1

1

6.

Moles of NaOH ((line 4) × (line 5)) / 1000

0.001

0.0015

0.0013

7.

Moles of acid

0.001

0.0015

0.0013

8.

Weight of Replaceable Hydrogen ((line 7) × 1.008)

0.001

0.0015

0.0013

9.

% Replaceable hydrogen ((line 8) × 100)) / (line 1)

0.2

0.29

0.25

10.

Average % Replaceable Hydrogen

0.25

11.

Average deviation in parts per thousand

120

± 0.03

Show your calculations for calculating the average deviation in an appendix: |0.2 – 0.25| = 0.05 |0.29 – 0.25| = 0.04 |0.25 – 0.25| = 0

| 0.05 + 0.04 + 0|/3= 0.03

0.001

.

%

STRONG ACID – STRONG BASE REPORT SHEET

Q2: What are the correct steps to fill a burette while performing a titration that requires more than 50 mL?

Fill the burette, then perform the experiment and make sure the meniscus stays above 50 ml. then fill the burette to see the marking better and record initial volume. Then conduct the experiment and the second final volume should be recorded. The total volume used is calculated using the following equation. Total volume (mL) = (final 1 - initial 1) + (final 2 - initial 2)

Q3: Potassium hydrogen phthalate is hygroscopic. How would using a jar that was left open for a significant period of time affect your results? If the jar was left open KHP will attract more water from the atmosphere since it is a hygroscopic substance. This will result in lower concentration of KHP, and the solution will be heavier because of the absorbed water. The molar content will be lower.

STANDARDIZATION OF 0.1 M HCl SOLUTION TRIAL #1

TRIAL #2

TRIAL #3

1.

Volume of HCl solution (mL)

25

25

25

2.

Final burette reading (in mL)

18.25

18.75

18.85

3.

Initial burette reading (in mL)

0.65

1.10

1.25

4.

mL of NaOH used

17.6

17.65

17.6

5.

Average Molarity of NaOH

0.1168

0.1168

±

±

0.0011

±

0.1168

0.0011

(line 5, previous page) 6.

Moles of NaOH ((line 5) x (line 4)) / 1000

0.002

0.007

0.007

7.

Moles of HCl

0.002

0.007

0.007

8.

Molarity of HCl = ((line 7) x 1000)) / (line 1)

0.08

0.28

0.28

9.

Average Molarity

0.21

10.

Average deviation in parts per thousand

430

Show your calculations for calculating the average in an appendix: |0.08 +0.28+0.28|/3 = 0.21

± 0.09

M

0.0011

Q4: If your pipette was wet when you started to use it, how would your results be affected, if: a) it was wet with distilled water; b) it was wet with NaOH; c) it was wet with 1 M HCl; d) it was wet with your 0.1 M HCl

a) The concentration of the HCI solution that was added from the pipette would be lower than 0.1 M HCI. The observed concentration would be lower than the actual concentration. b) The HCI solution in the pipette would be neutralized before it is added to the flask. This results again in the observed concentration being lower than the actual concentration. c) Since the pipette is wet with a higher concentrated HCI solution, the solution would have a higher concentration than 0.1 M HCI. The observed concentration would be higher than the actual concentration. d) If the pipette is wet with 0.1 M HCI, then the solution in the flask added from the pipette with have the same concentration of 0.1 M HCI. Therefore, the observed concentration will be accurate and matching the actual concentration.

POTENTIOMETRIC TITRATION OF HCl WITH NaOH Trial

Burette Reading

Total volume of NaOH added (mLs)

Solution pH

0.00

1.22

2.

1.15

1.23

3.

3.21

1.25

4.

5.18

1.35

5.

7.12

1.42

6.

9.16

1.52

7.

10.56

1.62

8

12.31

1.75

9.

13.98

1.94

10.

16.21

2.07

11.

17.16

2.26

12.

18.01

3.65

13.

19.12

7.65

14.

19.63

9.16

15.

20.25

10.09

16.

20.31

10.42

17.

20.50

10.71

18.

20.63

10.94

19.

20.71

11.09

20.

22.21

11.56

21.

24.15

11.77

22.

25.75

11.90

23.

27.89

12.01

24.

30.05

12.10

25.

32.52

12.16

26.

34.12

12.21

27.

36.21

12.25

28.

38.16

12.28

29.

39.81

12.31

1.

(Initial)

From the graph: Equivalence point titre =

20.6

pH at the Equivalence point =

0.47

mL of NaOH

Therefore the molarity of the HCl solution = Molarity NaOH solution x Equiv. Point Titre Volume of HCl solution = |0.1168 x 20.6| / 25

= 0.096

Compare this value for the molarity of the HCl solution with that obtained in Part D. What is the absolute difference between your two results?

The value of molarity of HCI solution is 0.21 M and it is larger than the value I calculated from the graph data. The absolute difference between my two results is 0.114.

Q5: Write an introduction for the Strong Acid Base experiment as if this was a formal lab. Please ensure that you include any pertinent equations, techniques, and terminology.

Acids are substances that produce hydrogen ions in water and bases are substances that produce hydroxide ions in water. A strong acid is one that completely ionizes in water. One mole of a strong acid (HA) dissolves in water yielding one mole of H+ and one mole of the conjugate base

(Mott). A strong base is one that is able to deprotonate very weak acids in an acid-base reaction (Mott). The dissociation of water is described by the equilibrium: H2O + H2O  H3O+ + OH In the equilibrium above, water is an amphoteric substance. It acts as both acid and base. Standardization is the Process of determining the exact concentration of a solution (Eddy). The purpose of this lab is to perform the standardization of 0.1 M HCl and 0.1 M NaOH. Acid-base titrations are used to determine the unknown concentration of an acid or base by neutralizing it with an acid or base of known concentration (Mott). Potentiometric titration is a laboratory method that was used during the experiment. This method does not include any chemical indicators but measures the electrical potential of a substance(Admin, 2019). The strong base is dispensed using a burette. A pH scale was used as an acid-base indicator in the lab. pH is a scale used to specify the acidity or basicity of an aqueous solution. the digital reading on the pH meter is proportional to log [H3O+]. At the end of the experiment, a graph should be plotted. This graph indicates where the equivalence point is in the acid-bas titration. The equivalence point is the point in titration where the amount of titrant added is enough to completely neutralize the analyte solution (Anne Marie Helmenstine). The study of strong acid-base is important as most enzymes can only do their job at a certain acidity level. Every time food is digested, acids and bases are at work in the digestive system. To fully understand how the human body and many other organisms operate, a good knowledge on strong acid-bases is a must.

Bibliography:

Admin. (2019, June 26). What is Potentiometric Titration, its Principle, Method, Types. Retrieved July 22, 2020, from https://byjus.com/chemistry/potentiometric-titration/

Anne Marie Helmenstine, P. (n.d.). Here's What the Equivalence Point Means in Chemistry. Retrieved July 22, 2020, from https://www.thoughtco.com/definition-of-equivalence-point605101

Eddy, D. (n.d.). Chemistry 104: Standardization of Acid and Base Solutions. Retrieved July 22, 2020, from http://www.chem.latech.edu/~deddy/chem104/104Standard.htm

Foundation, C. (n.d.). 12 Foundation. Retrieved July 22, 2020, from https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/1.20/primary/lesson/acids-andbases-in-biology-bio

Mott, V. (n.d.). Introduction to Chemistry. Retrieved July 22, 2020, from https://courses.lumenlearning.com/introchem/chapter/strong-acid-strong-base-titrations/

The dissociation of water. (n.d.). Retrieved from https://groups.chem.ubc.ca/courseware/pH/section3/index.html

STRONG ACID – STRONG BASE GRADING SHEET TO BE INCLUDED WITH YOUR REPORT NaOH Standardization ITEM Calculation of Molarity

MAX. MARK

Proper use of Significant Figures

2 2

Calculation of Average Deviation

1

Precision of Results

3

Q1: Elimination of a trial

2

YOUR MARK

Analysis of Unknown Acid ITEM

MAX. MARK

Calculation of % Replaceable Hydrogen

1

Proper use of Significant Figures

1

Calculation of Average Deviation

1

Precision of Results

3

Accuracy of Results

2

Q2: Filling a burette

1

Q3: Hydroscopic KHP

1

YOUR MARK

HCl Standardization ITEM

MAX. MARK

Calculation of Molarity

2

Proper use of Significant Figures

2

Calculation of Average Deviation

1

Precision of Results

3

Q4: Wet pipette

2

YOUR MARK

Potentiometric Titration ITEM

MAX. MARK

Graphs

6

Q5: Formal Introduction

4

YOUR MARK

Mark: Comments:

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