Archive – AP Chem – Q2 – week 4 – 21-22

Q2: Week 4 – 12/6 – 12/10

Jump to: Tuesday, Wednesday, Thursday, Friday ^{______________________________________________________________}

12/6 – Monday – A Day – A Day – 2/3a Lab, 4

Main focus –

a) To review the the TUMS Lab design of back titrations and solutions needed.

b) To review the Standardization of NaOH with KHP.

c) To complete the standardization of NaOH with KHP.

Period 2/3:

1. Complete the review of the design of the TUMS Lab

2. Complete the review of the Standardization of NaOH.

3. The Standardization of NaOH with KHP Titration.

Period 4:

1. Complete the review of the Standardization of NaOH.

2. The Standardization of NaOH with KHP Titration.

Today’s Notes:

Standardization of the Strong base in this back titration of TUMS.

In this analysis of the “active ingredient” of Tums ( CaCO₃ ) we will need to use a strong base to titrate the excess HCl that was used to drive the reaction to completion:

Net Ion: 2H⁺ (aq) + CaCO₃(s) —> CO₂ (g) + H₂O (l) + Ca⁺²

Excess

The excess Strong Acid will drive the reaction to completion due to Le Chateliers Principle. It also important to to have excess Strong Acid to react with all the CaCO₃that will be mixed and “hidden” with the binder, coloring, flavor, and etc. That is why it is important to crush the tablets (tabs!) with a mortar and pestle in order to expose all of the salt, CaCO₃to the acid.

Now after we add the excess acid we will have to Titrate this excess acid with a Strong Base. This lab produces incredibly accurate results ONLY IF OUR SOLUTIONS that we use ARE ACCURATE. We are adding 0.04 moles of protons from the 100.0 ml of a 0.4 M HCl solution. Because we are adding about 0.01 moles of extra protons from the strong acid we need to titrate the excess protons with a strong base AND that solution needs to verified or STANDARDIZED.

I made a 0.5 M NaOH solution. I was very careful to make this solution BUT because strong Bases are very reactive that solution is definitely LOWER in concentration as the hydroxide reacts with the CO₂ (Lewis Acid) in the air. I used 20 grams of solid NaOH (.5 mole) dissolved in a 1 liter of solution to make a 0.50 M NaOH solution

BUT not all of the solid is NaOH as CO₂from the air will cause the NaOH to become Na₂CO_{3. This also happens in solution. Strong bases are carbon dioxide scrubbers that are used to remove it from space capsules.}

2NaOH(s) + CO₂(g) —–> Na₂CO₃ + H₂O

Also NaOH is deliquescent which means it can absorb water from the air and start dissolving itself. This would add weight to the Base and dilute is quantity.

Because NaOH has these issues we need to verified or STANDARDIZE it with a weak acid that is not reactive and does not have these issues. A perfect solution to this (no pun intended!) is using KHP. Potassium Hydrogen Phalate.

KHP, (KHC₈H₄O₄) is excellent to standardize a Strong Base with because it

1. Weak Acid – thus does not react unless forced to by a Strong Base

2. Is a solid – we eliminate volume errors when making this solution

3. It has a large molecular mass (204 g/mol) – measurement errors with a large

molecular mass will not lead

to large mole errors.

Net Ion: HC₈H₄O₄^– + OH^– —-> C₈H₄O₄^{– 2}+ H₂O

You will find from this standardization that my solution of 0.50 M NaOH is less but we need to know its exact value to proceed with the lab.

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12/06 – Monday Homework: –

1. Please continue with the formal write-up of the TUMs lab. You should be able to get farther with the procedure as everyone was able Standardize the Strong Base to verify the strength of the base.

I made a 0.50 M NaOH solution but one group today found it was 0.482 M which makes sense as the base solution is very reactive and deliquescent.

a) Background – A full page single typed. There is so much to write about. Do not forget to direct your discussion toward the Objective (which is to determine the milligrams of calcium carbonate in TUMS).

b) Detailed written procedure – There are 3 parts to your procedure.

( I will be scrutinizing your procedure and the conclusion)

The procedure has 3 parts-

1) Design of the lab.

2) Preparation of chemicals necessary to perform Back – Titration on 2 tabs of

750 mg TUMS (calcium carbonate = active ingredient)

Please use my video below to help with this below if needed:

a) KHP solution – used solid reagent

b) Excess acid solution – started with 1.o M HCl stock solution

c) Strong Base solution (for back titration) – started with solid reagent

3) Actual Steps taken to perform the lab in order to calculate the mg of active ingredient in 2 tabs of TUMs.

a) Standardization

b) tablet preparation

c) Titrations, etc.

c) calculations – Neatly presented – . INCLUDE ALL REACTIONS!!!

d) data table (typed) INCLUDING SUBSCRIPTS!!!!!!!

Example: HC₈H₄O₄^– NOT HC8H4O4-

DESIGN YOUR DATA TABLE, BASED ON YOUR STEPS in the procedure that describes what you need to do to completely determine the milligrams of calcium carbonate in your TUMS tablet.

This will help you understand the Lab better and give you a head start to what we will do Monday when we Titrate the TUMs.

e) Results –

f) Conclusion – Please describe all errors and completely analyze you errors. It is a very accurate lab, all volumetric titrations are if the done precisely with standardized chemicals, However they are numerous errors to discuss and analyze.

Also try to discuss why your tablets milligrams of CaCO₃ was not 750 mg in terms of the company that makes them (GSK).

g) Sources

End of Monday!!!

Solution Review for the Tums lab:

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12/7 – Tuesday – B Day – 2, 3b/4 Lab

Main focus –

a) To perform a back titration in determining the milligrams of calcium carbonate in TUMS – Lab 13

Period 2:

1. Complete the Standardization of NaOH if necessary – Compare the Standardized molarity

2. Crush 2 tabs of Tums, add water, measure 100 ml of 0.40 M HCl, add to crushed tabs,

3. Back Titrate.

Period 3/4:

1. Complete the Standardization of NaOH if necessary – Compare the Standardized molarity

2. Crush 2 tabs of Tums, add water, measure 100 ml of 0.40 M HCl, add to crushed tabs,

3. Back Titrate. 4. Calculate the mg of CaCO3 per tablet.

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12/7 – Tuesday Homework: –

1. Please complete the calculations for Lab 13 to determine the mg of CaCO3 in each tablet of TUMS. You may need to view my videos below that reviews the calculations to complete.

2: Complete the Procedure (3 parts) AND Calculations for the Formal write-up in the shared drive. The lab write-up requirements are posted above under Monday’s homework. Remember that all calculations and chemical reactions need to be written and presented neatly.

TUM Lab Calculations Review –

Screencast TUMS Lab Calculations Review – An older video that reviews calculations

END OF TUESDAY.

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12/8 – Wednesday – A Day – A Day – 2/3a Lab, 4

Main focus –

a) To calculate the milligrams of calcium carbonate in a tablet of Tum

b) To identify and explain the errors in Lab 13 – Tums Lab

c) T0 begin the design of the Lab 14 – Determination of aspirin in a Bayer Tablet.

Period 2/3:

1. Tums Lab Calculations Review

2. Tums Labs Lab error analysis

3. Aleve Form – This is based on a Back Titration (just like you would to for the next Lab).

Period 4:

1. Tums Labs Lab error analysis

2. Aleve Form – This is based on a Back Titration (just like you would to for the next Lab).

Aleve Form Classwork – Work together in Lab groups to complete the following Form that will help understand your TUMs lab and help with the aspirin lab that we will be the next lab..

Please use the hardcopies of the form to help complete. This form is based on a design of a lab for another over the counter medication that will be very similar to the aspirin (BUT NOT THE SAME) that we will begin soon. Remember that you will be using a back titration as the active ingredient in Advil (Naproxen) is a weak (acid or base). Use your procedure in the TUMS lab to help solve this form which is about the calculations and steps needed to complete the quality control lab of the active ingredient of AleveTM .

The form will be on auto- reply and you have 3 replies individually. I will hand out the handwritten when everyone has completed their responses from both classes.

Quality Control Aleve Form.pdf
View Download

ALEVE Quality Control Lab FORM:

End of Thursday….

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12/8 – Wednesday Homework: –

1. Complete the TUMS lab with a Results section and a conclusion. Conclusions DO NOT INCLUDE ANOTHER PROCEDURE!! Your conclusion will include the the explanation of the data written in your results sections. It will include error analysis. This is a very accurate lab but there are places in the procedure that error COULD of occurred. Please try to evaluate those possible instances AND HOW THEY explain YOUR results. How have the amount of errors in this experiment been controlled or limited? What was done to maximize accuracy? Do not just state this was an accurate lab. You need to explain why!

Everyone determined that the amount of active ingredient was UNDER the reported value (750 mg per tablet). What are the implications of this quality control experiment considering that our errors have been controlled or limited in our design of the experiment. What does your outcome as the quality control chemist mean for the consumer or the company.

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12/9 – Thursday – B Day – 2, 3b/4 Lab

Main focus –

a) To complete the review of the TUMS lab through the class Aleve activity (form)

a) To begin the design of Lab 14.

Period 2:

1. We will complete the Aleve form in class.

2. A review of the reactions in Lab 14 if time is permitted.

Period 3/4:

1. We will complete the Aleve form in class.

2. A review of the reactions in the Bayer (aspirin) lab.

3. Students design of the Lab 14 will begin.

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Lab 14 – The Determination of aspirin in a Bayer tablet

Lab 14 will be a lab and a test. You will be graded on how your lab group will design a lab (back titration) to determine the milligrams of aspirin in a single bayer tablet. You will design the lab in the same fashion as I designed the TUMS lab using YOUR arbitrary values that you design.. Last weeks form of Alleve you completed an assignment that was a theoretical lab that determined the milligrams of another active ingredient. You may want to revisit that form or its key. Hint: Both are weak acids.

You will determine the milligrams of aspirin by using 2 tablets of Bayer. Please look at the molecular structures of aspirin below to begin your lab design. Acetylsalicylic acid (aspirin) gets hydrolyzed into 2 components in water.

This is a slow reaction that can be increased by temperature and excess chemical (Le Chateliers principle).

Identification of organic acids can done by Table R in our Regents Chemistry reference tables:

The mechanism for the hydrolysis of aspirin is as follows:

Lab 14 – Aspirin Lab Test Requirements:

a: Using the Google Doc that is shared individually that I have sent, start determining the procedure necessary to determine the amount of aspirin in a Bayer tablet.

USE THE TUMS LAB AS A GUIDE and the Aleve form as your guide!

b: Understanding Lab 13 will help here. You need to figure out what chemicals you need and what their Molarities will need to be to successfully titrate aspirin.

You will need to complete preliminary calculations that will determine the theoretical amount of the other chemicals needed to perform the titration, in the same fashion as we did with Lab 13.

c: You will perform the titration and determine the milligrams of the active ingredient per tablet as a lab group in a later date.

d: I will look over your procedure and preliminary calculations and give you the go ahead to perform the Lab test.

e: In your Shared Lab group Doc, I expect

In this Lab Test I am require the following:

1. Title Page.

2. Objective.

3. materials

4.a detailed procedure

a) Design of lab – (arbitrary values decided on)

b) Calculations and steps to make certain solutions required in Lab.

c) Steps in the actual lab

5. Data Table

6) typed calculations page that report the milligrams of aspirin. Tablet the final result. (DO NOT FORGET ANY CHEMICAL REACTIONS!)

No Background, Results section or Conclusion necessary!

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12/9 – Thursday Homework: –

1. Please complete the TUMS Lab.

2. Please start your design of the Aspirin Lab.

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12/10 – Friday – A Day – A Day – 2/3a Lab, 4

Main focus –

a) To design a lab (14) that will determine the mg of aspirin in a tablet of Bayer.

Period 2/3:

1. Complete the Aleve Form is not done already and review with the key:

Volumetric Titration Practice Aleve Key p.pdf
View Download

2. Design Lab 14, make solutions, start the lab?

Period 4:

1. Design Lab 14, make solutions, start the lab?

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Lab 14 – The Determination of aspirin in a Bayer tablet

This is a slow reaction that can be increased by temperature and excess chemical (Le Chateliers principle).

Identification of organic acids can done by Table R in our Regents Chemistry reference tables:

The mechanism for the hydrolysis of aspirin is as follows:

What does aspirin do? It block the productions of prostaglandins. It is another example of NSAIDS. Non-steroidal anti-inflammatory drugs

First lets review last weeks form – Alleve:

Volumetric Titration Practice Aleve TEST Key p.pdf
View Download

Lab 14 – Aspirin Lab Test Requirements:

a: Using the Google Doc that is shared individually that I have sent, start determining the procedure necessary to determine the amount of aspirin in a Bayer tablet.

USE THE TUMS LAB AS A GUIDE and the Aleve form as your guide!

b: Understanding Lab 13 will help here. You need to figure out what chemicals you need and what their Molarities will need to be to successfully titrate aspirin.

You will need to complete preliminary calculations that will determine the theoretical amount of the other chemicals needed to perform the titration, in the same fashion as we did with Lab 13.

c: You will perform the titration and determine the milligrams of the active ingredient per tablet as a lab group in a later date.

d: I will look over your procedure and preliminary calculations and give you the go ahead to perform the Lab test.

e: In your Shared Lab group Doc, I expect

In this Lab Test I am require the following:

1. Title Page.

2. Objective.

3. materials

4.a detailed procedure

a) Design of lab – (arbitrary values decided on)

b) Calculations and steps to make certain solutions required in Lab.

c) Steps in the actual lab

5. Data Table

6) typed calculations page that report the milligrams of aspirin. Tablet the final result. (DO NOT FORGET ANY CHEMICAL REACTIONS!)

No Background, Results section or Conclusion necessary!

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12/10 – Friday Homework: –

1. Complete the TUMS lab. The lab requirements for the formal write-up is posted above under Monday’s Homework. Please complete the Lab write-up in the shared doc that I have previously sent you.

2. Complete your design of Lab 14 in the shared doc that I am sending you.