Archive – Q1 week 1 – 19-20
Week of 11/4 – 11/8 – Please Refresh every time you open– this page is changing often!
11/5 – Monday – period 2-
1. RAT #1 Acid Base Intro Basics
period 2/3 –
demo straw /washing soda/ indicator..
1. RAT #1 Acid Base Intro Basics
2.
Stiochiometry 5a – Acid Base Reactions new classwork worksheet.
Stiochiometry 5a – Acid Base Reactions new Key.pdf
3. Acid Bases Pre – Titration classwork worksheet and review with key below.
11/4 – Monday Homework – Read Carefully- Test 3 tomorrow!
1. Lab 6 – is due Tuesday- comments will be completed by Monday afternoon.
2. Please review the Today’s RAT . Expect a new Rat Tomorrow that will include the same information but includes acid/base stoichiometry which your homework is based on!
It will count as a TEST 3 in quarter 1!!! I will take the better of the 2 RATS as Test 2!!!
.
Rat #1 – Acid Base Intro Basic Review: You probably do not need too much of this as you reviewed in class
when you took the group portion of the quiz.
This video has timecode buttons under the description to move to the question you need to review.
You will have to play in Youtube to see the descriptions!
Acid Base Stoichiometry –
3: Please complete Acid Bases Pre – Titration worksheet and review with key below. Period 4 may have started this worksheet already but please complete it.
4. Please complete the SIDE 1 –
Stiochiometry 5a – Acid Base Reactions new.pdf worksheet with (side 1 only! ) using the posted video below.
This is a lesson in writing Net Ion Acid/Base Reactions!
*Remember that soluble salts (aq) were never written together in NET ION EQUATIONS while the precipitate (s) are because they do exist in a crystal together. In Acid/Base the “soluble ” compound is the “Strong” Acid or Base because they completely dissociate just like soluble salts, however weak acids and bases are NOT completely dissociated thus must be written together. WATER IS A NEVER Written dissociated because they barely dissociate!!!
Tutorial on Stoichiometry 5a – Acid Base Reactions new.pdf worksheets:
New Side One Lecture : Acid/Base Net Ion Reaction Review:
Okay i made an error on the last net ion reaction. The product of NH3 and H3O+ is NH4+ and water (H2O)! Sorry about that! I was trying to illustrate the reaction between a Strong Acid (H3O+) and a weak base (NH3) thus water would be made in the neutralization reaction. (Thanks Josh Kaplan 2018)
11/5 – Tuesday period 2/3 –
1. RAT #2 Acid Base Intro Basics and Stiochiomety – TEST 3 – Counts for 1st Quarter!!!
Lab:
2. Lab 9 – Strong Acid/Base Volumetric Titration
with phenolphthalein & pH probes
period 4 –
1. RAT #2 Acid Base Intro Basics and Stiochiomety – TEST 3 – Counts for 1st Quarter!!!
2. Lab 9 – Strong Acid/Base Volumetric Titration
with phenolphthalein & pH probes – INTRO
11/5 – Tuesday – Homework:
1. Period 2/3 – students
a) Review your TEST 2 – with key posted in Power School
b) Complete Lab 9 on your Graph with the instructions and video posted below:
Here are today’s Logger Pro Files (data collected):
You need Logger Pro installed in your computer to view files:
It might be easy to see the actual pH or volume from the file if your printed graph is not clear.
2. Period 4 students –
a)
Review your TEST 2 – with key posted in Power School
b)Please complete side 2 of
Stiochiometry 5a – Acid Base Reactions new.pdf worksheet.
I have posted the key and or the video below for your review.
New Side 2 Lecture : Acid/Base Titration problems:
Lab 9 INSTRUCTIONS-
In this Lab we were trying to determine the concentration of a the strong acid solution using a KNOWN concentration of a STRONG Base.
Thus 50.0 ml of Strong Acid (HCl) in the small beaker was titrated with 0.06M Strong Base , Ca(OH2).
Objectives –
On the Printed graph please number your work!
1: Determine the concentration of the acid.
2: Determine the equivalence point of the titration. (Identify of the graph)
3: Determine the end point of the titration. (Identify on the graph)
4: Determine the halfway equivalence point. (Identify on the graph)
5: Confirm the final pH of the titration.
6: Confirm the initial pH of the titration.
7: On the four points of the titration curve, (initial pH, final pH, equivalence point, halfway equiv.)
determine the percentage of the Acid/Base
8: Write the net-ion reaction.
Please use the lecture below AND THE KEY to the video to complete the lab directly on the printed Titration Graph of the Strong base/Strong Acid that you did today.
LAB 9 : Strong Base – Strong Acid Titration lab write-up:
The video uses the same titration but a different amounts and concentrations.
In this Video I am using 0.03 M of Ca(OH)2 and 25 ml of unknown concentration of HCl. I have posted a key for this video so that you can see my calculations for this specific titration. Again you used 0.06 M Ca(OH)2 not 0.03 M and we started with 50.0 ml HCl in the beaker and added a total of 50 ml of base at the conclusion of the titration.
Key for this assignment: Remember that I am using different concentrations and volume in this titration but the Acid and Base are the same. You should be able to follow how I calculated my values for THIS titration curve and apply to your values you obtained today,
End of Tuesday…
11/6 – Wednesday –
*Best out of 2 RATS became extra credit for Test 2 (1st quarter)
Best RAT grade out of 2 –> multiply by .1 then take the square root = extra points added to Test 2
period 2 –
Connect Rat To Titrations-
1. Do not hand in Lab 9 – Strong Acid (HCl) was titrated with 0.06M Strong Base (Ca(OH)2)
We need to compare this graph with a new titration today.
2. Lab 10 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
We will complete this titration right away and print out graphs.
3. Back at our seats and we will compare and contrast both graphs, and I will walk you through how to complete this Lab.
What is similar and dissimilar with these titrations?
a) Starting pH b) Ending pH c) size of the asymptote? d) pH at equivalence e) Buffer region
What is new with this titration?
a) How to determine the Ka from the half equivalence point
b) Describing the pH at the equivalence point – Why is not at 7? We will calculate this in the spring.
4 Henderson Hasselbalch Derivation – Maybe
– period 3/4
Connect Rat To Titrations-
1. Lab 9 titration – Strong Acid (HCl) was titrated with 0.06M Strong Base (Ca(OH)2)
2. Complete the Lab 10 at seats together as a class. Lab 10 instructions posted under Tuesday above.
3. Lab 10 titration –
Lab 10 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
4. Back at our seat we will compare and contrast both graphs, and I will walk you through how to
complete this Lab.
What is similar and dissimilar with these titrations?
a) Starting pH b) Ending pH c) size of the asymptote? d) pH at equivalence e) Buffer region
What is new with this titration?
a) How to determine the Ka from the half equivalence point
b) Describing the pH at the equivalence point – Why is not at 7? We will calculate this in the spring.
Henderson Hasselbalch Derivation – Maybe
LAB 10 – Requirements
Lab 10 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
Objectives –
On the Printed graph please number your work!
1: Determine the concentration of the acid.
2: Determine the equivalence point of the titration. (Identify of the graph)
3: Determine the end point of the titration. (Identify on the graph)
4: Determine the halfway equivalence point. (Identify on the graph)
5: Confirm the final pH of the titration.
6: Confirm the initial pH of the titration. YOU CANNOT DO THIS STEP!!!!!!!(In the spring)
7: On the four points of the titration curve, (initial pH, final pH, equivalence point, halfway equiv.)
determine the percentage of the Conjugate Acid/ Conjugate Base / OH–
8: Write the net-ion reaction.
9: Determine the Ka of the Acid.
Lab 10: Lecture: If you want me to walk you through all steps. I will go over step 9 in class tomorrow.
Wednesday NOTES!
**ACID/BASE TITRATION Curve NOTES:
The new skills that we learned from Monday’s/ Tuesday’s Titrations are identifying the parts of a Titration curve. The striking part of the Titration graph is the asymptotic line that occurs as the pH changes becomes exponential changes as the pH nears the equivalence point.
We learned the endpoint in an Acid/Base titration is really an approximation of the equivalence point. The endpoint refers to the volume of titrant added (Standard Base Yesterday) and pH that results when the chemical indicator changes color. This color change will never be exactly at the equivalence point but it approximates the volume of titrant added if the indicator has a color change on the asymptotic line.
Consider 2 titrations like the 2 we did yesterday. We used phenolphthalein which has a color change (turns from colorless to pink at pH changes of 8 – 9). What if we used Thymol blue or Methy red?
|
Table M  |
Do not forget that these indicators are themselves conjugate acid base pairs in equilibrium.
In the case of Thymol blue  |
Notice in the first Titration which you should recognize as a strong acid / strong base titration, with a pH of the equivalence pH of 7, can utilize both Thymol blue and Methyl red as indicators as the endpoints will be on the asymptotic line. They would have endpoints with approximately the same
volume as the equivalence point.
In the second titration you should recognize as as weak acid / strong base titration because the starting pH is greater and the equivalence point pH is NOT 7! In this titration the asymptotic line is not quite as long thus Methy Red would no longer be appropriate to use because its color change would occur at MUCH different volume than the equivalence point volume resulting in a very poor approximation of the volume needed by the titrant to neutralize the acid. It would lead to undervalued concentration of the acid in this case. THymol blue however would however lead to very good approximation of the equivalence volume because its color change is closer to the equivalance point.
Notice both the Titrations have an equivalence volume of 50 ml of base added, illustrating that both acids are at the same concentration even though the acid in the titration on the right is a weaker acid. The Strong Base DRIVES the weak acid to COMPLETION like the Strong Acid on the Left does naturally.
Remember the Volume at the equivalence point is what is normally needed to attain the concentration of the solution being titrated (acid in both cases above and in our lab 10 and 11). This volume of added titrant (chemical with known concentration) is used to determine the concentration of the solution in the beaker under the buret.
The new skill that we added in our graphical analysis of acid base titrations allows us to determine the Ka of acid, or conjugate acid (produced from a base that is titrated).
Remember Ka is really a Keq which is a equilibrium constant that expresses whether the products or reactants are favored. I have been surprised how many students have asked what this in the past few days? We have discussed that Keq in terms of thermodynamics when we talked about spontaneity which if you remember is pathway that the universe supports. A favorable pathway always is supported by a dispersion of energy from a concentrated source (increase in entropy).
Reactants ó Products
Since Keq generally = [Products] / [Reactants]
Then a Keq greater than 1 is a reaction that has more Products than Reactants at equilibrium.
If there are more products present at equilibrium then THE FORWARD DIRECTION is more favorable pathway then the reverse reaction (which would build up reactants if more favorable).
The forward reaction then is more spontaneous!
Strong Acids have an incredibly large Keq because virtually all of the acid dissociates to leave virtually zero reactants which would drive the Keq to a VERY LARGE NUMBER! Strong Acids dissociate very spontaneously!
HCl ð H+ + Cl–
Keq = [H+][Cl–] / [HCl]
Keq = VERY LARGE
Weak acids have an incredibly small Keq because virtually all of the acid remains undissociated and thus there are less products and more reactants. Weak acids dissociate very UNspontaneously!
HC2H3O2 ó H+ + C2H3O2–
Keq = [H+][C2H3O2–] / HC2H3O2
Keq = Very Small
Now because these reactions are very similar (HA ð H+ + A– ) we call them Ka!
Keq = Ka when we deal with acids dissociating.
We can find the Ka graphically because of the relationship between Ka and what it equals:
Using this relationship we know that when we have equal amounts of conjugate Base (A–) and conjugate acid (HA) the log [A–] / [HA] will go to zero because the log of 1 = 0 !!
Thus when [A–] = [HA] pH = pKa
and we can get the pKa of acid which is just the -log of the Ka. Once we have the pKa we just
perform the 10-x calculation to attain the Ka of the acid.
How do we find the point where the conjugate Base (A–) and conjugate acid (HA) are equal
We find the half equivalence point!!!
 |
So once we establish the equivalence point which is in the middle of the asymptote we attain the volume at that point which in the example to the left is 20 ml. Now we take the equivalence volume and halve it: 20 ml / 2 = 10 ml 10 ml represents the volume of titrant (base) added to neutralize half of the acid. This point is where half of the weak acid has been converted to the conjugate base. So if we had 1 mole of weak acid, .5 moles of the weak acid remains and .5 moles of conjugate base has been created. This is the point where the acid = conjugate base ! pH of this point = pKA |
So in the above example the pH at the Half – equivalence point is equal to 3. Pka of the acid = 3.
The Ka of the acid is thus: 10-3 = 1 x 10-3
This is a Ka of a weak acid because it is less than 1 which means the reactants or the undissociated acid ( HA ) is a larger quantity because the reverse reaction is more spontaneous.
11/6 – Wednesday – Homework
Period 2 class ONLY: Try and complete LAB 9 ONLY!!!
We collected data from Lab 10 today and we will complete it in class tomorrow!!
Optional: Review your Acid/Base RAT
1. Period 2 Class please
complete side 2 of
Stiochiometry 5a – Acid Base Reactions new.pdf worksheet.
I have posted the key and or the video below for your review.
Link to the Video for side 2 of the Stiochiometry 5a – Acid Base Reactions new.pdf worksheet.
2. Read todays Notes posted above.
3. View the lecture posted below and follow along with me using the Determining pKa and Indicators.pdf worksheet below. Try the last question at your own risk and I will review in class. (you do not have to do it).
Lab 9 Thursday 11/8
Period 3/4 class ONLY:
1. Complete Lab 9 (what we did today directly on the graph).
Use the instructions posted on Tuesday for lab 9 . We did a lot together in class to start.
* You need to understand every objective or point (#) of this lab!
2. Please complete with me the Determining pKa and Indicators.pdf worksheet. I will post a lecture that will review this worksheet. Try the last question at your own risk and I will review in class. (you do not have to do it).
New Skills
pKa = pH at half equivalence point
a) determining Ka of Acid Graphically
b) determining indicator based on pKa
c) Henderson – Hasselblach equation derivation
Determining pKa and Indicators.pdf Lecture video:
End of Wednesday finally!.
11/7 – Thursday- period 2/3-
1. Review homework skills related to Lab 10-
a) Derivation of Henderson-Henderson Equation: pKa is like pKw.
b) Using half equivalence point to determine Ka of acid from graph and H-H equation.
BUFFER REGION!
c) determining the best acid base indicator using pKa’a and NOT ph FOR END POINTS!!!
2. Complete Lab 10 – Weak Acid – Strong Base Titration – We will complete together in class.
Compare and contrast both Titrations.
period 4 –
1. Lab 9 – review last point – Determine the end points of the titration if we used phenolphthalein.
2. Review homework skills related to Lab 10-
a) Derivation of Henderson-Henderson Equation: pKa is like pKw.
b) Using half equivalence point to determine Ka of acid from graph and H-H equation.
BUFFER REGION!
c) determining the best acid base indicator using pKa’a and NOT ph FOR END POINTS!!!
3. Lab 10 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
–Collect Data – Homework is to use today’s skills to complete Lab 10.
LAB 10 – Requirements
Lab 10 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
Titrant: 0.06M Strong Base, Ca(OH2)
Analyte: HC2H3O2
Objectives –
On the Printed graph please number your work!
1: Determine the concentration of the acid.
2: Determine the equivalence point of the titration. (Identify of the graph)
3: Determine the end point of the titration. (Identify on the graph)
4: Determine the halfway equivalence point. (Identify on the graph)
5: Confirm the final pH of the titration.
6: Confirm the initial pH of the titration. YOU CANNOT DO THIS STEP!!!!!!!(In the spring)
7: On the four points of the titration curve, (initial pH, final pH, equivalence point, halfway equiv.)
determine the percentage of the Conjugate Acid/ Conjugate Base / OH–
8: Write the net-ion reaction.
9: Determine the Ka of the Acid.
Lab 10: Lecture: If you want me to walk you through all steps.
11/8 – Thursday – Homework:
All Students:
1. Please complete this worksheet that was given out in class today. It resembles what your acid /base test next Tuesday will look like. It encompasses all the skills that we have learned!!
I would try it alone and then use the key to help OR JUST LET ME WALK YOU THROUGH THE worksheet with the lecture below.
*Period 4 students will have a bit more trouble with this assignment because we did not complete lab 10 yet. So please try to dig in and try to make sense of the solutions. I will make this MUCH clearer tomorrow.
Lecture : Acid Base Lab Titration Graph Questions.pdf worksheet
End of Thursday..
Strong Acid/Strong Base Titration: For review.
Titrant: NaOH
Analyte: HCl
Weak Acid/Strong Base Titration: For review.
Titrant: NaOH
Analyte: HC2H3O2 – (vinegar!) Ka = 1.8 x 10-5
Weaker Acid/Strong Base Titration: For review.
Titrant: NaOH
Analyte: NH4Cl – (ammonium chloride) Ka = 5.7 x 10-10
11/8 – Friday – period 2
1. Review of homework:
2. complete last question on this worksheet.
3. Completed The Design a Titration with HF and NaOH
4. Lab 11: Weak Base / Strong Base Titration – GATHER DATA
period 3/4
1. Lab 10 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
Titrant: 0.06M Strong Base, Ca(OH2)
Analyte: HC2H3O2
2. Complete Lab 10 in class on printed titration graph.
3. Completed The Design a Titration with HF and NaOH worksheet.
Video review of the Design a Titration with HF and NaOH: I did this together with period 2 folks.
I will do this for period 4 folks tomorrow!
Friday – Weekend Homework:
1. You are to complete the form below once you have reviewed you test.
Here is a Blank copy of the form you could print:
2: Review your work in the form as it will automatically grade and send back a link to a handwritten key.
3. Study for test Next Tuesday using the ACID BASE STUDY POINTS posted below:
TEST review Form:
ACID BASE STUDY POINTS:
1. Identify Arrhenius, Bronsted- Lowry , Lewis ACID Bases
2. Ka Table – strengths of acid – You will be given this table
3. Identifying conjugate acid/bases.
Conjugate Acid Base Pairs and Complex ions new.pdf
4. Identifying Strong Acids and Strong Bases.
5. Basic ph skills – converting to ph, converting [ ] from pH, etc
Skills 1 – 5 are from the intro worksheets and BOTH RATS:
6. Neutralization problems (Pre- neutralization worksheet)
7. Strong Acid base titration skills – Lab 9 – Lecture posted Tuesday
8. Weak Acid/ Strong Base titration skills – Lab 10 – Lecture posted Wednesday and Thursday
9. Picking an appropriate indicator – Lecture posted Wednesday with NOTES.
10. Calculating the Ka from graph – Lecture posted Wednesday and NOTES.
11. Writing Net Ion reactions
12. AP question example – todays classwork – Lecture posted above
End of week 1….