Columbia University Titration Chemistry Lab Report

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mm16267

Science

Columbia University in the City of New York

Description

Experiment 11: Titration

Procedure

A. Preparation of Sodium Hydroxide Solution

In a beaker prepare 300mL of 0.10M sodium hydroxide from the solid. Record the mass of the sodium hydroxide to as many decimal places as you can.(Note how the numbers on the balance are increasing.)Be sure to stir it well!

B. Standardization of Sodium hydroxide solution

1. Weigh out about 0.15g of solid oxalic acid and dissolve it in about 20mL of deionized water inan Erlenmeyer Flask. Record the actual mass.

2.Add about 5 drops of phenolphthalein to the solution.

3. Clean a burette and rinse it out with deionized water.With the stopcock open, run some of your sodium hydroxide solution down the inside and allow it to drain. Fill your burette with your sodium hydroxide solution and record the volume.Make sure there are no air bubbles, especially in the tip.

4. Titrate the sodium hydroxide into the acid solution until the color changes and record the final volume.

5.Repeat this procedure three times.

C. Determination of Unknown

1. Obtain a test tube of unknown hydrochloric acid and record the unknown number.

2. Using a volumetric pipette, add 10.00mL of your unknown to an Erlenmeyer flask.

3. Add a few drops of phenolphthalein.

4. Titrate with your standardized sodium hydroxide from part B recording the initial and final volumes.

5. Repeat this procedure for a total of three trials.(If there is not enough unknown to do three trials of 10.00mL each, use 5mL for the last trial.Obtain a 5 mL volumetric pipette for the sample.)

DISPOSE OF YOUR NEUTRALIZED SOLUTIONS IN THE BLUE WASTE CONTAINER.

DISPOSE OF THE LEFTOVER ACID IN THE YELLOW WASTE CONTAINER.
DISPOSE OF THE LEFTOVER BASE IN THE PINK WASTE CONTAINER.

Links to Procedural Videos:

Procedure Part B:

Procedure Part C:

Name_____________________________________________Section ____________________

Experiment 12

Titration

A. Preparation of Sodium Hydroxide Solution

Mass of sodium hydroxide desired (show work) ________

Mass of sodium hydroxide used _____________

B. Standardization of Sodium Hydroxide Solution (Show Work)

Balanced chemical equation:____________________________________________________

Trial 1Trial 2Trial 3

Mass of oxalic acid__0.1445 g___0.1520 g___0.1489 g_

Initial burette reading__0.64 mL___0.14 mL___1.24 mL_

Final burette reading_22.55 mL__22.75 mL__23.25 mL_

Volume NaOH added _____________________________

moles of oxalic acid_____________________________

moles of NaOH added_____________________________

Molarity of NaOH_____________________________

Average Molarity__________

C. Determination of Unknown (Show Work)

Balanced chemical equation:___________________________________________

Unknown number _NA_____

Trial 1Trial 2Trial 3

Volume of unknown HCl

titrated_10.00 mL__10.00 mL__10.00 mL_

Initial burette reading __1.50 mL___0.28 mL_ __2.23 mL_

Final burette reading_34.85 mL__33.60 mL_ _35.70 mL_

Volume NaOH added__________ __________________

moles NaOH added ____________________________

(Use average molarity from part B

and multiply it by the volume you added)

moles HCl____________________________

molarity of HCl____________________________

Average molarity__________

Actual Molarity (from instructor) __0.3665M_

percentage error ___________

QUESTIONS:

1.From the SDS, what is another name for sodium hydroxide?

2. Why will the phenolphthalein eventually fade?Show reactions.

3.Why do we titrate into a flask instead of a beaker?

4. What effect would each of the following errors have on the determined concentration of the unknown acid? (Would the calculated value be too high, too low or unchanged?) Explain your reasoning in each case.

a. The mass of the oxalic acid was recorded to low.

b. The unknown acid was added to a flask containing 35 mL of water.

c. The final volume in the standardization was recorded too high.

d. The final volume in the determination of the unknown acid was recorded too low.


5. The concentration of an unknown sample of sulfuric acid was determined by the method used in this experiment, using two sets of titrations.In the first titration the sodium hydroxide was standardized by titrating 0.1852g of oxalic acid dihydrate (molar mass = 126.07g/mole) with 32.30mL of sodium hydroxide solution.In the second titration 10.00mL of the unknown sulfuric acid solution was titrated with 12.85mL of the sodium hydroxide solution.What was the concentration of the sulfuric acid?(Show your work!!)

Discussion:

Discuss why your calculated value for the unknown differs from the acutal.List of all possible sources of error and what can be done to avoid these errors.

Unformatted Attachment Preview

Experiment 11: Titration Procedure A. Preparation of Sodium Hydroxide Solution In a beaker prepare 300mL of 0.10M sodium hydroxide from the solid. Record the mass of the sodium hydroxide to as many decimal places as you can. (Note how the numbers on the balance are increasing.) Be sure to stir it well! B. Standardization of Sodium hydroxide solution 1. Weigh out about 0.15g of solid oxalic acid and dissolve it in about 20mL of deionized water in an Erlenmeyer Flask. Record the actual mass. 2. Add about 5 drops of phenolphthalein to the solution. 3. Clean a burette and rinse it out with deionized water. With the stopcock open, run some of your sodium hydroxide solution down the inside and allow it to drain. Fill your burette with your sodium hydroxide solution and record the volume. Make sure there are no air bubbles, especially in the tip. 4. Titrate the sodium hydroxide into the acid solution until the color changes and record the final volume. 5. Repeat this procedure three times. C. Determination of Unknown 1. Obtain a test tube of unknown hydrochloric acid and record the unknown number. 2. Using a volumetric pipette, add 10.00mL of your unknown to an Erlenmeyer flask. 3. Add a few drops of phenolphthalein. 4. Titrate with your standardized sodium hydroxide from part B recording the initial and final volumes. 5. Repeat this procedure for a total of three trials. (If there is not enough unknown to do three trials of 10.00mL each, use 5mL for the last trial. Obtain a 5 mL volumetric pipette for the sample.) DISPOSE OF YOUR NEUTRALIZED SOLUTIONS IN THE BLUE WASTE CONTAINER. DISPOSE OF THE LEFTOVER ACID IN THE YELLOW WASTE CONTAINER. DISPOSE OF THE LEFTOVER BASE IN THE PINK WASTE CONTAINER. Links to Procedural Videos: Procedure Part B: https://www.youtube.com/watch?v=no4j_j-35c4 Procedure Part C: https://www.youtube.com/watch?v=mTG_V7HHtg4 Name_____________________________________________ Section ____________________ Experiment 12 Titration A. Preparation of Sodium Hydroxide Solution Mass of sodium hydroxide desired (show work) ________ Mass of sodium hydroxide used _____________ B. Standardization of Sodium Hydroxide Solution (Show Work) Balanced chemical equation: ____________________________________________________ Trial 1 Trial 2 Trial 3 Mass of oxalic acid __0.1445 g_ __0.1520 g_ __0.1489 g_ Initial burette reading __0.64 mL_ __0.14 mL_ __1.24 mL_ Final burette reading _22.55 mL_ _22.75 mL_ _23.25 mL_ Volume NaOH added __________ __________ _________ moles of oxalic acid __________ __________ _________ moles of NaOH added __________ __________ _________ Molarity of NaOH __________ __________ _________ Average Molarity __________ C. Determination of Unknown (Show Work) Balanced chemical equation: ___________________________________________ Unknown number _NA_____ Trial 1 Trial 2 Trial 3 Volume of unknown HCl titrated _10.00 mL_ _10.00 mL_ _10.00 mL_ Initial burette reading __1.50 mL_ __0.28 mL_ __2.23 mL_ Final burette reading _34.85 mL_ _33.60 mL_ _35.70 mL_ Volume NaOH added __________ _________ _________ moles NaOH added __________ (Use average molarity from part B and multiply it by the volume you added) _________ _________ moles HCl __________ _________ _________ molarity of HCl __________ _________ _________ Average molarity __________ Actual Molarity (from instructor) __0.3665M_ percentage error ___________ QUESTIONS: 1. From the SDS, what is another name for sodium hydroxide? 2. Why will the phenolphthalein eventually fade? Show reactions. 3. Why do we titrate into a flask instead of a beaker? 4. What effect would each of the following errors have on the determined concentration of the unknown acid? (Would the calculated value be too high, too low or unchanged?) Explain your reasoning in each case. a. The mass of the oxalic acid was recorded to low. b. The unknown acid was added to a flask containing 35 mL of water. c. The final volume in the standardization was recorded too high. d. The final volume in the determination of the unknown acid was recorded too low. 5. The concentration of an unknown sample of sulfuric acid was determined by the method used in this experiment, using two sets of titrations. In the first titration the sodium hydroxide was standardized by titrating 0.1852g of oxalic acid dihydrate (molar mass = 126.07g/mole) with 32.30mL of sodium hydroxide solution. In the second titration 10.00mL of the unknown sulfuric acid solution was titrated with 12.85mL of the sodium hydroxide solution. What was the concentration of the sulfuric acid? (Show your work!!) Discussion: Discuss why your calculated value for the unknown differs from the acutal. List of all possible sources of error and what can be done to avoid these errors.
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Explanation & Answer

I decided to assume the oxalic acid used to standardize the NaOH solution was the dihydrate form (that's mentioned in problem 5 and fits the experimental data better). Please see the attached file. Ask questions if you have any.

Experiment 11: Titration
Procedure
A. Preparation of Sodium Hydroxide Solution
In a beaker prepare 300mL of 0.10M sodium hydroxide from the solid. Record the mass
of the sodium hydroxide to as many decimal places as you can. (Note how the numbers on the
balance are increasing.) Be sure to stir it well!
B. Standardization of Sodium hydroxide solution
1. Weigh out about 0.15g of solid oxalic acid and dissolve it in about 20mL of deionized
water in an Erlenmeyer Flask. Record the actual mass.
2. Add about 5 drops of phenolphthalein to the solution.
3. Clean a burette and rinse it out with deionized water. With the stopcock open, run
some of your sodium hydroxide solution down the inside and allow it to drain. Fill your
burette with your sodium hydroxide solution and record the volume. Make sure there are
no air bubbles, especially in the tip.
4. Titrate the sodium hydroxide into the acid solution until the color changes and record
the final volume.
5. Repeat this procedure three times.
C. Determination of Unknown
1. Obtain a test tube of unknown hydrochloric acid and record the unknown number.
2. Using a volumetric pipette, add 10.00mL of your unknown to an Erlenmeyer flask.
3. Add a few drops of phenolphthalein.
4. Titrate with your standardized sodium hydroxide from part B recording the initial and
final volumes.
5. Repeat this procedure for a total of three trials. (If there is not enough unknown to do
three trials of 10.00mL each, use 5mL for the last trial. Obtain a 5 mL volumetric pipette
for the sample.)
DISPOSE OF YOUR NEUTRALIZED SOLUTIONS IN THE BLUE WASTE
CONTAINER.
DISPOSE OF THE LEFTOVER ACID IN THE YELLOW WASTE CONTAINER.
DISPOSE OF THE LEFTOVER BASE IN THE PINK WASTE CONTAINER.

Links to Procedural Videos:
Procedure Part B: https://www.youtube.com/watch?v=no4j_j-35c4
Procedure Part C: https://www.youtube.com/watch?v=mTG_V7HHtg4

Name_____________________________________________ Section ____________________
Experiment 12
Titration
A. Preparation of Sodium Hydroxide Solu...


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