Archive – Q2 week 1 – 20 – 21
Week of 11/16 – 11/20 – Please Refresh every time you open– this page is changing often!
The 4 day – A, B, C, D cycle looks like this:
Day Period
2 3 4
In class: A Lab Lab Single Class
Remote: Lab Lab Single Class
In class: B Single Class LAB LAB
Remote: Single Class LAB LAB
Monday In class: C Single Class LAB LAB
Remote: Single Class LAB LAB
In class: D Lab Lab Single Class
Remote: Lab Lab Single Class
This weeks 5 day Schedule:
11/16 – Monday – “C” Day – period 2, – I 2(A,C) 3(A) AP CHEMISTRY
–period 2, – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 3,4 (LAB) – I. 3(C) 4(A,C) AP CHEMISTRY
-period 3,4 (LAB) – R 3(C) 4(A,C) REMOTE INSTRUCTION
11/17 – Tuesday- “D” Day – period 2,3 (Lab) – I 2(B,D) 3(D) AP CHEMISTRY
– period 2,3 (Lab) – R 2(B,D) 3(D) REMOTE INSTRUCTION
-period 4 – I 3(B) 4(B,D) AP CHEMISTRY
-period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION
11/18 – Wednesday “A” Day – period 2,3 (Lab) – I 2(A,C) 3(A) AP CHEMISTRY
–period 2,3 (Lab) – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 4 – I 3(C) 4(A,C) AP CHEMISTRY
-period 4 – R 3(C) 4(A,C) REMOTE INSTRUCTION
11/19 – Thursday- “B” Day –period 2, – I 2(B,D) 3(D) AP CHEMISTRY
– period 2, – R 2(B,D) 3(D) REMOTE INSTRUCTION
-period 3,4 (LAB) – I 3(B) 4(B,D) AP CHEMISTRY
-period 3,4 (LAB) – R 3(B) 4(B,D) REMOTE INSTRUCTION
11/2o – Friday – “C” Day – period 2, – I 2(A,C) 3(A) AP CHEMISTRY
–period 2, – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 3,4 (LAB) – I. 3(C) 4(A,C) AP CHEMISTRY
-period 3,4 (LAB) – R 3(C) 4(A,C) REMOTE INSTRUCTION
11/16 – Monday – “C” Day – period 2, – I 2(A,C) 3(A) AP CHEMISTRY
–period 2, – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 3,4 (LAB) – I. 3(C) 4(A,C) AP CHEMISTRY
-period 3,4 (LAB) – R 3(C) 4(A,C) REMOTE INSTRUCTION
The RED team and the Green Team are Remote today. Please move to the Remote Instruction Page.
Period 2, Period 3
1. I have entered your grade from the weekends homework (Strong Acid Strong Base Form) into the 2nd quarter.
Some of you did not add after I corrected the key. If you do not have a grade for this form it is because I do not
have a submission AFTER I FIXED my ERROR in the key. If you are not getting my REMIND posts then you
need to sign up!
2. Lab 10 is not due yet – We will use it to compare this titration with the next one LAB 11 – Weak Acid Strong Base.
Lab 11 – Weak Acid Strong Base Titration (virtual)-
Lab 11 – Weak Acid (HC2H3O2) titrated with 0.12M Strong Base, NaOH
What is similar and dissimilar with the STRONG ACID STRONG BASE (LAB 10) titration?
a) Starting pH b) Ending pH c) size of the asymptote? d) pH at equivalence e) Buffer region
What is new with this titration? – Notes below!
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.
c) Henderson Hasselbalch Derivation – Maybe
Period 4: – Recorded and posted later
1. A walk through of the Weak Acid Strong Base Lab:
LAB 11 – Requirements
Lab 11 – Weak Acid (HC2H3O2) titrated with 0.06M Strong Base, Ca(OH2)
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
11/16 – Monday – “C” Day – Homework –
1. Please complete the Lab 11 – Weak Acid Strong Base titration.
Lab 11 – 25.0 ml of Weak Acid (HC2H3O2) titrated with 0.12M Strong Base, NaOH
If you were not present for Period 4 today please view today’s lecture posted below:
Period 4 – Lab 11 Lecture:
2. Please complete the Weak Acid Strong Base Form posted below using the given
Titration graph:
You are going to complete the same work that you did with Lab 11 on a new titration graph that is also a Strong Acid Strong Base Titration. The titration uses the following:
25.0 ml of unknown concentration of HC2H3O2 is titrated with 0.03 M of Ca(OH)2.
Please use the graph below to complete in the same way that you completed lab 10.
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if bromthymol blue was used. (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.
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
Weak Acid Strong Base Form:
Monday NOTES- Included is the Derivation of the Henderson- Hasselbach equation:
**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.
End of Monday..
11/17 – Tuesday- “D” Day – period 2,3 (Lab) – I 2(B,D) 3(D) AP CHEMISTRY
– period 2,3 (Lab) – R 2(B,D) 3(D) REMOTE INSTRUCTION
-period 4 – I 3(B) 4(B,D) AP CHEMISTRY
-period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION
The Blue and Orange team are remote today. Please move to the remote instruction page.
Period 2, Period 4: Class lectures
1. Henderson – Hasselbach equation – Buffer region review.
a) solve for the Ka (of WEAK Acids) – How does the titration curve change with a smaller Ka?
b) solve for the pH (in the buffer region with different ratios of conjugate acid and conjugate base.
 |
The Blood buffers the blood pH so that
The main buffer in our blood that prevents large pH changes if the following conjugate acid base pair: Conjugate Acid Conjugate Base
|
The pKa of H2CO3 = 6.1 The Ka of this week acid = 10 –3.8 = 1.58 x 10-4
Blood is buffered at pH of about 7.4. What is the ratio of conjugate base to conjugate acid in this buffered solution?
pH = pKa + log [A–]/[HA]
7.4 = 6.1 + log [HCO3-1]/[H2CO3]
1.3 = log [HCO3-1]/[H2CO3]
10X to both sides of the equation
101.3 = [HCO3-1]/[H2CO3]
= 19.9 : 1 ratio
*Normal human blood has about a 20 : 1 ratio!
What would this look like on a titration curve?
Classwork: We have already completed questions 1a, 2a, 3a last week.
We will work on rest of the worksheet.
Acid Base Lab Titration Graph Questions.pdf
Period 3 Lab:
Lab 12 – Weak Acid (Hydrogen Phthalate) with Strong Base-
KHC8H4O4 NaOH
25 ml of an unknown hydrogen Phthalate with a 0.12 M NaOH.
We will complete this twice.
1. With a pH probe and print graph
2. With just an indicator – phenolphthalein.
LAB 12 – Requirements
Lab 12 – 25.0 ml of Weak Acid (KHC8H4O4) titrated with
25.0 ml of Strong Base, NaOH is titrated with 25.0 ml of 0.18 M Weak Acid (KHC8H4O4)
Today’s Class lesson:
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
10. Determine the initial concentration of the weak acid using the indicator titration And compare its value based on the END POINT to the value based on the EQUIVALENCE POINT!
11/17 – Tuesday- “D” Day – Homework–
1. Complete the worksheet below ( it was class work previously 1a – 1c) and review with the key.
The video below teaches the concepts covered in today’s lesson. It is not a complete review of he worksheet.
Acid Base Lab Titration Graph Questions.pdf
11/18 – Wednesday “A” Day – period 2,3 (Lab) – I 2(A,C) 3(A) AP CHEMISTRY
–period 2,3 (Lab) – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 4 – I 3(C) 4(A,C) AP CHEMISTRY
-period 4 – R 3(C) 4(A,C) REMOTE INSTRUCTION
The red team and the green team are remote today. Please move to the remote instruction page.
Period 2, Period 4: Class lessons
1. Review the homework –
a) Instead of pH ranges for the color changes for chemical indicators we can use pKa’s
They are also acid/base equilibrium systems
HIn <—> H+ + In–
and thus they also have Ka’s and pKa’s
What do you think the pKa can tell us about the acid/base indicators?
b) Titration of adding Strong Acid to Weak base differences
a) pH at the equivalence point –
Reaction during the titration – Driven by the strong Acid to completion to the equivalence point
H3O+ + C6H7O2– – –> HC6H7O2 + H2O
strong acid Weak Conjugate Base —> stronger conjugate acid
Reaction that occurs at the equivalence point – Equilibrium reached (NOT DRIVEN)
HC6H7O2 + H2O <—> C6H7O2-1 + H3O+
conjugate acid ionizes water Lowers pH at equilalence
| Strong Acid Strong Base ~Lab 10 |
pH = 7 @ equivalence | only spectators that do not ionize water |
| Weak Acid Strong Base ~Lab 11, 12 |
pH >7 @ equivalence | Conjugate Base produced reacts with water to produce OH- |
| Strong Acid Weak Base ~Last nights HW |
pH <7 @ equivalence | Conjugate Acid produced reacts with water to produce H3O+ |
b) buffer region and implications of the Henderson Hasselbach equation
Period 3 Lab:
1. We will perform a hands- on Acid/Base Titration: Lab 12
Lab 12 – Weak Acid (Hydrogen Phthalate) with Strong Base-
KHC8H4O4 NaOH
25 ml of an unknown hydrogen Phthalate will be titrated with a 0.12 M NaOH.
We will complete this twice.
1. With a pH probe and print graph
2. With just an indicator – phenolphthalein.
LAB 12 – Requirements
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
10. Determine the initial concentration of the weak acid using the indicator titration And compare its value based on the END POINT to the value based on the EQUIVALENCE POINT!
Today’s lesson:
11/18 – Wednesday “A” Day – Homework:
1. Please complete with me the Determining pKa and Indicators.pdf worksheet. Please review with key and or the posted video that reviews some parts of the worksheet worksheet.
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!.
11/19 – Thursday- “B” Day –period 2, – I 2(B,D) 3(D) AP CHEMISTRY
– period 2, – R 2(B,D) 3(D) REMOTE INSTRUCTION
-period 3,4 (LAB) – I 3(B) 4(B,D) AP CHEMISTRY
-period 3,4 (LAB) – R 3(B) 4(B,D) REMOTE INSTRUCTION
The BLUE team and the Orange team are remote today. Please move to the remote instruction page.
Period 2, Period 3 :
1. Graph a titration curve group quiz.
You will plotting the graph of the titration going in reverse of the calculations and skills you have developed from Labs 10,11, and 12.
a) Design a Titration that will reach the equivalence point when 30 .0 ml 0.15 M NaOH
is added to 20.0 ml of HF. A total of 50 ml of the titrant will be added.
You will need the Ka of the Acid = 3.5 x 10-4
b) You will have to estimate the initial pH (you need equilibrium skills that we will have in the spring).
c) You will have to estimate the equivalence point pH ((you need equilibrium skills that we will have in the spring).
The numbered objectives that must be numbered on your graph include:
1) Initial pH (estimated ph but not volume).
2) The half equivalence point
3) point on the graph when 20.0 m of the titrant is added (show work)
4) Equivalence point (estimated ph but not volume)
5) The final ph (show work)
You also need the:
6) Calculate the initial concentration of the HF (show work)
7) Net ion reaction of the titration
8) Equilibrium reaction at the equivalence that supports your estimated pH at point #4
9) from the following list of indicators AND their pKa’s Identify the most appropriate
indicator for the endpoint titration AND the ENDPOINT of the titration.
| p-Nitrophenol | 5.3 to 7.6 | 7.2 |
| Phenol red | 6.4 to 8.0 | 7.9 |
| Thymol blue | 8.0 to 9.6 | 8.9 |
Blank Worksheet:
Design a Titration with HF and NaOH new.pdf
Period 4 –
1. We will perform a hands- on Acid/Base Titration: Lab 12
Lab 12 – Weak Acid (Hydrogen Phthalate) with Strong Base-
KHC8H4O4 NaOH
25 ml of an unknown hydrogen Phthalate will be titrated with a 0.12 M NaOH.
We will complete this twice.
1. With a pH probe and print graph
2. With just an indicator – phenolphthalein.
LAB 12 – Requirements
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
10. Determine the initial concentration of the weak acid using the indicator titration And compare its value based on the END POINT to the value based on the EQUIVALENCE POINT!
11/19 – Thursday- “B” Day Homework –
1. Complete the titration curve group quiz.
2. THE RED TEAM and the BLUE TEAM must complete LAB 10, 11, and 12. Staple all Three together.
– Blue team hands these labs in tomorrow – Friday 11/20
– Red Team, Orange, Green hand in labs – Monday 11/23
11/2o – Friday – “C” Day – period 2, – I 2(A,C) 3(A) AP CHEMISTRY
–period 2, – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 3,4 (LAB) – I. 3(C) 4(A,C) AP CHEMISTRY
-period 3,4 (LAB) – R 3(C) 4(A,C) REMOTE INSTRUCTION
The red team team and the green team are remote today. Please move to the Remote Instruction page.
Period 2, Period 3
1. collect the Graph a titration curve group quiz.
2. Collect Lab 10, Lab 11, Lab 12 together, staple and hand in.
3. Complete the Acid Base 8 – Titrations worksheet
Period 4:
1. We will perform a hands- on Acid/Base Titration: Lab 12
Lab 12 – Weak Acid (Hydrogen Phthalate) with Strong Base-
KHC8H4O4 NaOH
25 ml of an unknown hydrogen Phthalate will be titrated with a 0.12 M NaOH.
We will complete this twice.
1. With a pH probe and print graph
2. With just an indicator – phenolphthalein.
LAB 12 – Requirements
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
10. Determine the initial concentration of the weak acid using the indicator titration And compare its value based on the END POINT to the value based on the EQUIVALENCE POINT!
Today’s lesson:
11/2o – Friday – “C” Day – Homework
1. You are to complete the Test review form below.
which is a review of all the concepts you need to complete the the acid base 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 Monday using the ACID BASE STUDY POINTS posted below:
4. Full remote students – Complete Lab 12 with video and graph below
TEST review Form:
FULL REMOTE STUDENTS:
Graph from today’s streamed Lab 12
Video from today’s Live STREAM of lab 12:
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
Key of the yesterday’s Graph a titration curve group quiz:
To be posted!
End of Monday..
REMOTE Instruction:
11/16 – Monday – “C” Day – period 2, – I 2(A,C) 3(A) AP CHEMISTRY
–period 2, – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 3,4 (LAB) – I. 3(C) 4(A,C) AP CHEMISTRY
-period 3,4 (LAB) – R 3(C) 4(A,C) REMOTE INSTRUCTION
The RED team and the Green Team are Remote today. Please move to the Remote Instruction Page.
Period 2 Zoom info:
Topic: AP Chemistry – 11.16 – Period 2
Time: Nov 16, 2020 08:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/86850676163?pwd=d1lRbkpLa21ZdjhrdDFJQUh0ejVBdz09
Meeting ID: 868 5067 6163
Passcode: 4DTQed
One tap mobile
+16465588656,,86850676163#,,,,,,0#,,568921# US (New York)
Period 3 Zoom info:
Topic: AP Chemistry – 11.16 – Period 3
Time: Nov 16, 2020 09:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/89165782820?pwd=S2JhenMvRnk1enExd0p2d2xvVHRlZz09
Meeting ID: 891 6578 2820
Passcode: sfv1vt
One tap mobile
+16465588656,,89165782820#,,,,,,0#,,852954# US (New York)
Period 2, Period 3 – Class Lesson
1. I have entered your grade from the weekends homework (Strong Acid Strong Base Form) into the 2nd quarter.
Some of you did not add after I corrected the key. If you do not have a grade for this form it is because I do not
have a submission AFTER I FIXED my ERROR in the key. If you are not getting my REMIND posts then you
need to sign up!
2. Lab 10 is not due yet – We will use it to compare this titration with the next one LAB 11 – Weak Acid Strong Base.
Lab 11 – Weak Acid Strong Base Titration (virtual)-
Lab 11 – Weak Acid (HC2H3O2) titrated with 0.12M Strong Base, NaOH
What is similar and dissimilar with the STRONG ACID STRONG BASE (LAB 10) titration?
a) Starting pH b) Ending pH c) size of the asymptote? d) pH at equivalence e) Buffer region
What is new with this titration? – Notes below!
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.
c) Henderson Hasselbalch Derivation – Maybe
Period 4: – Recorded and posted later
1. A walk through of the Weak Acid Strong Base Lab:
LAB 11 – 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 equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
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.
11/17 – Tuesday- “D” Day – period 2,3 (Lab) – I 2(B,D) 3(D) AP CHEMISTRY
– period 2,3 (Lab) – R 2(B,D) 3(D) REMOTE INSTRUCTION
-period 4 – I 3(B) 4(B,D) AP CHEMISTRY
-period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION
The Blue and Orange team are remote today. \
Period 2 Zoom info:
Topic: AP Chemistry – 11.17 – Period 2
Time: Nov 17, 2020 08:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/87482689874?pwd=aUdpQjgwaGJjVlF5Mk9UWUdFWW1sdz09
Meeting ID: 874 8268 9874
Passcode: Hdn23d
One tap mobile
+16465588656,,87482689874#,,,,,,0#,,886570# US (New York)
Period 4: Zoom info:
Topic: AP Biology – 11.17 Period 4
Time: Nov 17, 2020 09:30 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/89112471048?pwd=dFFtYlJDOU45NHFhUEptWHFST2dsUT09
Meeting ID: 891 1247 1048
Passcode: 6qUHqW
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Period 2, Period 4: Class lectures
1. Henderson – Hasselbach equation – Buffer region review.
a) solve for the Ka (of WEAK Acids) – How does the titration curve change with a smaller Ka?
b) solve for the pH (in the buffer region with different ratios of conjugate acid and conjugate base.
 |
The Blood buffers the blood pH so that Conjugate Acid Conjugate Base |
The pKa of H2CO3 = 6.1 The Ka of this week acid = 10 –3.8 = 1.58 x 10-4
Blood is buffered at pH of about 7.4. What is the ratio of conjugate base to conjugate acid in this buffered solution?
pH = pKa + log [A–]/[HA]
7.4 = 6.1 + log [HCO3-1]/[H2CO3]
1.3 = log [HCO3-1]/[H2CO3]
10X to both sides of the equation
101.3 = [HCO3-1]/[H2CO3]
= 19.9 : 1 ratio
*Normal human blood has about a 20 : 1 ratio!
What would this look like on a titration curve?
Classwork: We have already completed questions 1a, 2a, 3a last week.
We will work on rest of the worksheet.
Acid Base Lab Titration Graph Questions.pdf
Period 3:
Blue team can complete classwork /review with keys or video posted in
homework section.
The RED team is completing a hands-on titration that you will complete in your next lab period.
11/18 – Wednesday “A” Day – period 2,3 (Lab) – I 2(A,C) 3(A) AP CHEMISTRY
–period 2,3 (Lab) – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 4 – I 3(C) 4(A,C) AP CHEMISTRY
-period 4 – R 3(C) 4(A,C) REMOTE INSTRUCTION
The red team and the green team are remote today.
Period 2 Zoom info:
Topic: AP Chemistry – 11.18 – period 2
Time: Nov 18, 2020 08:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/84155900113?pwd=V1BwRkltc1RSNTBVbXdqcGhoYUEzZz09
Meeting ID: 841 5590 0113
Passcode: qg43gJ
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Period 4 Zoom Info:
Topic: AP Chemistry – 11.18 – Period 4
Time: Nov 18, 2020 08:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/88046114205?pwd=b1RUOEQ1cG5UU3l6ZkJlTzZBVFRvZz09
Meeting ID: 880 4611 4205
Passcode: tn04ku
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Period 2, Period 4: Class lessons
1. Review the homework –
a) Instead of pH ranges for the color changes for chemical indicators we can use pKa’s
They are also acid/base equilibrium systems
HIn <—> H+ + In–
and thus they also have Ka’s and pKa’s
What do you think the pKa can tell us about the acid/base indicators?
b) Titration of adding Strong Acid to Weak base differences
a) pH at the equivalence point –
Reaction during the titration – Driven by the strong Acid to completion to the equivalence point
H3O+ + C6H7O2– – –> HC6H7O2 + H2O
strong acid Weak Conjugate Base —> stronger conjugate acid
Reaction that occurs at the equivalence point – Equilibrium reached (NOT DRIVEN)
HC6H7O2 + H2O <—> C6H7O2-1 + H3O+
conjugate acid ionizes water Lowers pH at equivalence
| Strong Acid Strong Base ~Lab 10 |
pH = 7 @ equivalence | only spectators that do not ionize water |
| Weak Acid Strong Base ~Lab 11, 12 |
pH >7 @ equivalence | Conjugate Base produced reacts with water to produce OH- |
| Strong Acid Weak Base ~Last nights HW |
pH <7 @ equivalence | Conjugate Acid produced reacts with water to produce H3O+ |
b) buffer region and implications of the Henderson Hasselbach equation
Period 3 Lab:
Yesterday you completed the hand-on Titration for Lab 12 –
Please work on it using the following:
Lab 12 – Weak Acid (Hydrogen Phthalate) with Strong Base-
KHC8H4O4 NaOH
25 ml of an unknown hydrogen Phthalate with a 0.12 M NaOH.
We completed the titration 2 ways.
1. With a pH probe and print graph
2. With just an indicator – phenolphthalein.
LAB 12 – Requirements
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
10. Determine the initial concentration of the weak acid using the indicator titration And compare its value based on the END POINT to the value based on the EQUIVALENCE POINT that you determined graphically! (is it significantly different?)
Please move to the quarter one – week one page view tonights homework.
11/19 – Thursday- “B” Day –period 2, – I 2(B,D) 3(D) AP CHEMISTRY
– period 2, – R 2(B,D) 3(D) REMOTE INSTRUCTION
-period 3,4 (LAB) – I 3(B) 4(B,D) AP CHEMISTRY
-period 3,4 (LAB) – R 3(B) 4(B,D) REMOTE INSTRUCTION
The BLUE team and the Orange team are remote today.
Period 2 and Period 3 Zoom info: I will use the same meeting that I will keep open periods 2 – 4.
I am not sure why it tool so long for me to figure this out!
Topic: AP Chemistry 11.19
Time: Nov 19, 2020 08:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/85775921263?pwd=RWxVNkFCMDNHSFZEN1ZrZG16ZmROQT09
Meeting ID: 857 7592 1263
Passcode: hf9hEM
One tap mobile
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Period 2, Period 3 : Class lesson
1. Graph a titration curve group quiz.
You will plotting the graph of the titration going in reverse of the calculations and skills you have developed from Labs 10,11, and 12.
a) Design a Titration that will reach the equivalence point when 30 .0 ml 0.15 M NaOH
is added to 20.0 ml of HF. A total of 50 ml of the titrant will be added.
You will need the Ka of the Acid = 3.5 x 10-4
b) You will have to estimate the initial pH (you need equilibrium skills that we will have in the spring).
c) You will have to estimate the equivalence point pH ((you need equilibrium skills that we will have in the spring).
The numbered objectives that must be numbered on your graph include:
1) Initial pH (estimated ph but not volume).
2) The half equivalence point
3) point on the graph when 20.0 m of the titrant is added (show work)
4) Equivalence point (estimated ph but not volume)
5) The final ph (show work)
You also need the:
6) Calculate the initial concentration of the HF (show work)
7) Net ion reaction of the titration
8) Equilibrium reaction at the equivalence that supports your estimated pH at point #4
9) from the following list of indicators AND their pKa’s Identify the most appropriate
indicator for the endpoint titration AND the ENDPOINT of the titration.
| p-Nitrophenol | 5.3 to 7.6 | 7.2 |
| Phenol red | 6.4 to 8.0 | 7.9 |
| Thymol blue | 8.0 to 9.6 | 8.9 |
Blank Worksheet:
Design a Titration with HF and NaOH new.pdf
Period 4 – The green team will be doing the hands-on lab in class today.
1. Please complete the titration quiz above and upload to the shared doc that I have sent you this morning.
2. Please complete Labs 10 and 11. They will be handed in together with Lab 12 that you will work on in class tomorrow.
My full remote students – I will post a video for the lab 12 tomorrow.
Sorry I could not get it done today..
All three labs for full remote students will be due Monday.
11/2o – Friday – “C” Day – period 2, – I 2(A,C) 3(A) AP CHEMISTRY
–period 2, – R 2(A,C) 3(A) REMOTE INSTRUCTION
-period 3,4 (LAB) – I. 3(C) 4(A,C) AP CHEMISTRY
-period 3,4 (LAB) – R 3(C) 4(A,C) REMOTE INSTRUCTION
The red team team and the green team are remote today.
Zoom in for Period 2 and Period 3:
Topic: AP Chemistry – 11.20 – period 2,3, and 4
Time: Nov 20, 2020 08:00 AM Eastern Time (US and Canada)
Join Zoom Meeting
https://us02web.zoom.us/j/85913857214?pwd=L2RMOERNczNFczE2WEw2WTcvUzNNUT09
Meeting ID: 859 1385 7214
Passcode: T0xUkW
One tap mobile
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Period 2, Period 3
1. collect the Graph a titration curve group quiz.
2. Collect Lab 10, Lab 11, Lab 12 together, staple and hand in.
3. Complete the Acid Base 8 – Titrations worksheet
Period 4 and Full REMOTE STUDENTS:
Full remote students you will watch a live stream of a lab group completing the lab and use their data I will post their data this period.
1. The Orange and Full remote students will perform a hands- on Acid/Base Titration: Lab 12
The Green team can complete lab if you have not done already. It is due Monday with Lab 10 and 11. Please complete on the printed graph.
Lab 12 – Weak Acid (Hydrogen Phthalate) with Strong Base-
KHC8H4O4 NaOH
25 ml of an unknown hydrogen Phthalate will be titrated with a 0.12 M NaOH.
We will complete this twice.
1. With a pH probe and print graph
2. With just an indicator – phenolphthalein.
LAB 12 – Requirements
Objectives –
On the Printed graph please number your work!
1: Determine the equivalence point of the titration. (Identify of the graph)
2: Determine the concentration of the acid.
3: Determine the end point of the titration if phenolphthalein was used. (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.
10. Determine the initial concentration of the weak acid using the indicator titration And compare its value based on the END POINT to the value based on the EQUIVALENCE POINT!
FULL REMOTE STUDENTS:
Graph from today’s streamed Lab 12
Video from today’s Live STREAM of lab 12:
Please move to the week 1 page to view the weekends homework.