AP Chem – Q1 – week 2 – 26-27 | Mr. Grodski Chemistry

Q1: Week 2 – 9/7 – 9/11

<- Week 1 – Week 3 -> Jump to: Tuesday, Wednesday, Thursday, Friday

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LAB 1 – Activity of Metals Due Thursdays – 9/10

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9/7 – Monday – Labor Day

____________________________________ Jump to: Tuesday Homework / top 9/8 – Tuesday – A Day – 1AB

Main focus–

a) To apply Coulombs Law in Solubility and review the concept of spontaneity.

b) To review how to write a half reaction and identify a redox reaction.

c) To introduce the concepts of voltage and Net Potentials in redox reactions.

Period 1:

1. Lab 1 – Activity of metals – Page 4 – Classwork on Lab 1 – Half reaction practice / Observe the water/ reactions and depth of phenolphthalein color on the test tubes of Sn, Cu, Fe.

2. Note-taking on using the Solubility Rules, Coulombs Law, Spontaneity worksheet

The Solubility Rules, Coulombs Law, Spontaneity worksheet.pdf

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– molecules vs Salts (crystals)

– Charge Density and Table F in the Regents Chemistry Table

– Spontaneity in chemical reactions – pathways allowable by nature (universe)

3. Solubility using Coulombs Law – Questions 5 & 6.

KI & MgO dissolving demo

Solubility of KI:

#science totallygettingana+ from Tumblr For School (Probably)

How Salts dissolve – (Not a Redox reaction!)

__________________________________________________ jump to: top 9/8 – Tuesday Homework: –

1. Please view the Danielle Cell Lecture posted below. You may need to take notes.

2. Please make 2 submissions to the Daniell Form below. You have one more submission AFTER I will review this lesson Live in class Friday. You need to get as much as you can from this video and I will present it again Friday and take any questions! We do this together!

If you do not make your 2 submissions tonight then you will only have one for Wednesday.

3. Please complete Lab 1 activity of metals

1 – Daniell Cell lecture: This is for Tuesday’s homework:

_E⁰_{cell = NET VOLTAGE! (from redox reaction using the standard reduction potential table.}

positive voltage = spontaneous = there IS a pathway that the universe allows = IT REACTS!

negative voltage = non spontaneous = there is a NO pathway that the universe allows = IT doesn’t under the current set of conditions

Here is Danielle Cell Lecture Presentation that I use for this lecture

https://docs.google.com/presentation/d/e/2PACX-1vR82TNG2Bmo9EA-xTjEDQzPO341sEhJx4hzNxFKmZDKq13iphkhuoQ9rfT2I5ZGwCv5_RNOpbJE5Wky/pub?start=false&loop=false&delayms=3000

2 – Daniell Cell lecture: Form:

This form is based in the lecture above. You have 2 submissions this tonight It will be on auto-reply.

Loading…

__________________________________________ Jump to: Wednesday Homework / top 9/9 – Wednesday – B Day – 1, 2B

Main focus–

a) To better understand the Standard Reduction Potential Table and apply in to determine the Net E⁰cell – electromotor force (volts) for chemical reactions.

b) To review concepts of spontaneity, voltage, amperage through the Standard Reduction Table.

c) Review the concepts of the Daniell Cell (battery/voltaic cell) that includes spontaneity.

b) To built voltaic cell and test its voltage.

Period 1-2:

1. Half reactions practice – worked on Redox 4 – Net potentials Demonstrations worksheet

– half reactions and agents.

– net potentials —-> help us determine spontaneity

Redox 4 – Net potentials Demonstrations worksheet 1213.pdf
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Redox 4 – Net potentials Demonstrations worksheet 1213 key p.pdf

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2. Daniell Cell Review: Voltaic cells – (Danielle Cell) – in class demo/explanation

Danielle Cell Note-taking.pdf
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3. Lab 2 – Build voltaic Cells –

a) Review salt bridge in this battery.

b) Connect solubility concepts with ions in each half cell.

c) Introduce solubility and precipitation

d) Make observations and run radios

Standard Net Potential (E ⁰ cell) = voltages = potential difference = joules/C = Energy to move charge.

Voltages measure a pathway of electron flow (redox reactions) = Spontaneity = pathway! A pathway allowed by nature is driven by an increase in Entropy. Entropy is the measure of the dispersion on energy from a concentrated source to a less concentrated source.

This is the reason why Heat flows to Cold! or Stored Energy is eventually released OR Why a battery dies! Passive Transport! Entropy gives us Free energy!!! Is there really renewable energy?

_E⁰_{cell = NET VOLTAGE! (from redox reaction)}

positive voltage = spontaneous = there IS a pathway that the universe allows = IT REACTS!

negative voltage = non spontaneous = there is a NO pathway that the universe allows = IT doesn’t

under the current set of conditions

Standard Reduction Potential Table.pdf

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Cu in SnCl₂ Reaction vs. Sn in CuCl₂

Today’s Net Potential lesson: using the demonstration above.

__________________________________________________ Lab 2 – The Gerber Voltaic Cell

Voltaic Cell Lab 1 – Making of batteries (voltaic or galvanic cell) – In this Lab each person will make a pair of voltaic cells that if successfully created will power a 3 volt transistor radio.

LAB 2 – Voltaic Cell.pdf View Download

a) Made one voltaic cell and identifies anode, cathode and tested voltage.

Identified the spontaneous process with positive volts

wrote half reactions, identified ox and red agents.

b) Completed the diagram, conclusion questions, and reviewed errors for the writing of the

conclusion

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–Error Analysis for the conclusion:

Chemical reactions that may have contributed:

Mg + HOH (water) —–> Mg⁺² + 2OH^– + H₂ (g)

Would these ions (Mg⁺² + 2OH^–) form a precipitate with ions already present? The color of the entire battery was bluish? What does that say about movement of Cu⁺² ions?

What factors were competing? Based on the experimental voltage which factor dominated?

_____________________________________________ jump to: top 9/9 – Wednesday Homework: –

Lab 1 Due Tomorrow!

1. Please make one more submission to the Danielle Cell Lecture Form (Tuesday nights homework)

2. Watch the Voltaic Spontaneity lecture 2017 lecture below:

3. Complete the Voltaic Spontaneity Form below. You have 3 total submissions for this form and it is on auto-reply so make sure you have the correct email entered.

4. Complete the Conclusion for LAB 1. All I want is an explanation using atomic structure (number of protons in a row OR electron shells in columns) and Coulombs Law to explain the reactivity of Mg, Ca, Fe, and Sn ONLY!

Hint: Where are the metals that were tested in the periodic table in relation to each other?

For example: Element X is the smallest atom out of the 4 metals (Mg, Ca, Fe, and Sn) because it ( look at the trend of atomic radii in periodic table) thus it must have the greatest coulombic attraction to electrons which means it oxidizes the least.

2) – Voltaic Spontaneity lecture: This is for the homework form below..

The notes that I am using in the lecture are available here: (link: week 2 notes).

3) – Voltaic Spontaneity Form: This form is based in the lecture above.

Loading…

____________________________________________ Jump to: Thursday Homework / top 9/10 – Thursday – A Day – 1AB

Main focus –

a) To review concepts of spontaneity, voltage, amperage through the Standard Reduction Table.

b) Review the concepts of the Daniell Cell (battery/voltaic cell) that includes spontaneity.

c) To begin the discussion of Le Chateliers Principle.

Period 1:

1. Review the Danielle Cell Lecture Form- with key

Skills: Solubility, Spontaneity, Equilibrium,

How concentration of soluble ions in a voltaic cell affect its voltage.

Danielle Cell Lecture Form 25-26 – Key p.pdf View Download Voltaic Spontaneity Form 24-25 – Key p.pdf View Download

2. NO₂ and N₂O₄ ampule demo with heat, viewing the ampule as equilibrium.

Manipulating the spontaneity with heat, in phase changes, adding salt to ice

3. Revisit the Classroom Daniell cell and predict voltage: See Diluting demo lecture below

a) Diluting the Reduction half cell ( Cu/Cu⁺² ) or Blue One with water.

b) Diluting the Oxidation half cell (Zn/Zn+2) or clear bleaker with water.

4. Le Chateliers Principle/ with worksheet – Did not get to.

Le Chateliers principle worksheet p.pdf

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Le Chateliers principle worksheet KEY 2012 p.pdf
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LeChateliers Principle Notes:

Notice that concentration of the NO₂is large initially and decreases as the reaction proceeds.

Notice the initial concentration of N₂O₄ is zero (it has not been made yet) and increases as the reaction proceeds.

Both NO₂and N₂O₄ eventually level out and at this point equilibrium has been reached!

If the rate of 2NO₂combining to make N₂O₄ (forward reaction) is as fast as rate of N₂O₄ decomposing into 2NO₂ (reverse reaction) then the concentration of both chemicals become CONSTANT at equilibrium.

At point C, there 100% NO₂ and 0% N₂O₄ thus there is no competing reaction because there is no NO₂to combine to make the N₂O₄. The reverse reaction is at it maximum spontaneity and the forward reaction is at its minimum. There is a Shift in the reaction to move in the reverse. Over time its spontaneity will steadily decrease until it reaches the point of equilibrium and the “death of the reaction”.

Notice that the equilibrium position is at the bottom!! This is where the death of the reaction or where there is ZERO Spontaneity or No more release of energy into the Universe.

ΔS_universe = 0

At point A we have 100% NO₂and 0% N₂O₄. At this point there is tremendous pathway to go forward! There is No competing backwards reaction!! The reverse reaction is impossible here. It so spontaneous in the forward that the reverse is impossible!

At point B, there is 60% NO₂ and 40% N₂O₄.
Here we have a competing reaction reverse reaction thus the forward reactions is not as spontaneous and the reaction is getting closer to its death. The reverse reaction is still not as spontaneous as the forward but it is closing in, thus the overall Net direction is still forward but this pathway is not nearly as great as point A.

LeChatelier’s Principle and the Voltaic Cell NOTES:

– Classroom Danielle cell and predict voltage: See Diluting demo lecture below

a) Diluting the Reduction half cell ( Cu/Cu⁺² ) or Blue One with water.

By adding water to the Cu⁺² ion solution (molarity) decreased and thus the

Voltage Decreased!!!!

Explained in terms of LeChatelier’s Principle and Spontaneity!

Stress Response

⬇︎ [Cu⁺²] ⬆︎[Cu⁺²]

We added more water to dilute and lower the The reaction responds to undo the stress by

concentration of copper ions. moving toward equilibrium (in the reverse).

*We were lowering a reactant concentration by dilution and the reaction reacted by making more of the reactant to get to equilibrium.

Zn⁰ (s) + Cu⁺² —–> Zn⁺² + Cu⁰

^{Stress: decrease}

^Response:^{<—————–}^{Shift = voltage drop!}

^{(lowers spontaneity of forward reaction)}

^{Zn0 (s) + Cu+2 <—- Zn+2 + Cu0}

^{⬆︎ ⬆︎ ⬇︎ ⬇︎}

The reverse is favored more (than it was originally) which LOWERS the forwards reactions pathways or spontaneity, which results in lowering the voltage!

In terms of spontaneity:

b) Diluting the Oxidation half cell (Zn/Zn+2) or clear bleaker with water.

By adding water to the Zn⁺² ion solution (molarity) decreased and thus the

Voltage Increased!!!! Explained in terms of LeChateliers Principle and Spontaneity!

Stress Response

⬇︎[Zn⁺²] ⬆︎[Zu⁺²]

We added more water to dilute and lower the The reaction responds to undo the stress by

concentration of zinc ions. moving toward equilibrium (in the forward).

Zn⁰ (s) + Cu⁺² —–> Zn⁺² + Cu⁰

^{Stress: decreases}

^Response:^{Shift ———————> = Voltage increase!}

^{(increases spontaneity of forward reaction)}

We can decrease the concentration of dissolves ions (aq) another way besides adding water. We can precipitate out an ion if we add another salt that delivers an ion that will make an insoluble salt.

The homework for the weekend will have this concept.

LeChatelier’s Principle Lesson :

LeChateliers Lesson: Using the Ampules of NO2 and N2O4

Today’s Voltaic Cell Le Chatelier’s Demo:

Diluting the concentrations in the Danielle Cell Demo:

___________________________________________________ jump to: top 9/10 – Thursday’s Homework: –

1. Complete selected questions from the Le Chateliers Principle worksheet (front side) given out in class and review the key below. (Please complete questions 1, 4, 7). If you need help with this concept please watch the LeChatelier’s Principle Lesson posted above.

LeChateliers principle worksheet p.pdf
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LeChateliers principle worksheet KEY 2012 p.pdf
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2. Please complete Complete QUESTION 2 ONLY of the Intro Voltaic Cells Worksheet 2.

Intro Voltaic Cells worksheet 2 – skills.pdf

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3. Review question 2 (the one you just did) with the key below.

Intro Voltaic Cells worksheet 2 – skills Key p.pdf
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4. And/or you can follow along with me going over Question 2 with lecture below.

Intro Voltaic Cells worksheet 2 – skills.pdf worksheet Lecture:

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4) AP Chemistry Voltaic Cell Concepts Review worksheet 2 Video:

Click on the video below and it will START AT 23:12 to view explanation to the solution to question 2.

________________________________ Jump to: Friday Homework / top
9/11 – Friday – B Day – 1, 2B

Main focus–

a) To Complete the LeChateliers Concept with all stressors (concentration, temperature, pressure, volume, and the common ion effect).

b) To identify the precipitate in a net ion equation using the solubility rules or concepts.

c) To write a net – ion reaction for a precipitation reaction

d) To identify the voltage change in a voltaic cell due to Le Chatelier’s Principle with changes in the concentrations of ions in half cells, specifically when a precipitate is made or a common ion is added.

Period 1-2:

1. Complete the LeChateliers principle concepts with all stressors and the worksheet

– Keep connecting to the U diagram- See LeChateliers Lesson posted above.

LeChateliers principle worksheet KEY 2012 p.pdf
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– Connect this with the homework (question 2):

Intro Voltaic Cells worksheet 2 – skills Key p.pdf
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2. Precipitation reaction demo – Double replacement reactions or precipitation reactions-

Net ion reaction written to eliminate spectators!

Net Ion Reaction Intro – Precipitation 1920.pdf
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A) Wrote the precipitation reaction between lead (II) nitrate and potassium nitrate.

We used the following worksheet:

B) Particular Diagrams

C) Identified the precipitate using solubility rules (Table F)

3. Revisit the Classroom Daniell cell and predict voltage: See Diluting demo lecture below

a) Increase concentration of [Cu⁺²] in the Reduction half cell ( Cu/Cu⁺² ) or Blue One with water.

b) Creating a precipitate in the Oxidation half cell (Zn/Zn+2) or clear bleaker with water.

4. Lab 2 – voltaic Cells –

a) Write Objectives

b) Write half reactions and complete conclusion questions

c) Complete conclusion questions and analyze the errors

b) Begin the conclusion

Precipitation Demonstration:

Todays Notes: – Video of today’s demo posted below the notes

Revisit the Classroom Daniell cell and predict voltage by making the Zn⁺² ions precipitate out with Na₂CO₃ being added to the Zn/Zn⁺² half cell.

*By adding Na₂CO₃ I was really delivering CO₃^–2 ions to the oxidation half cell because Na₂CO₃ is soluble due to the group one ion (Na⁺) that has weak Coulombic attractions with the CO₃^–²in the salt (ionic compound).

Na₂CO_3 (s) → 2 Na⁺(aq) + CO₃^-2(aq) ↑

carbonate ion

Then CO₃^-2reacted with Zn⁺²to form a precipitate, which takes Zn⁺²out of the solution.

Net ion reaction: Zn⁺² (aq) + CO₃^-2(aq) → ZnCO₃ (s) which is a precipitate = insoluble!

Why does the carbonate ion produce a precipitate with the zinc ion?

Coulombs Law!!!

Lowering the Zn⁺² will cause the overall reaction in the Daniell cell to “shift” Right or be move spontaneous in the forward direction increasing the voltage.

Zn⁰ (s) + Cu⁺² —–> Zn⁺² + Cu⁰

^{Stress: decreases}

^{Response: Shift —————–>}

^{The forward reaction is now more favorable or spontaneous than the reverse thus}

^{the voltage increases (becomes more positive)!}

Daniell Cell – Le Chateliers Demo: Today’s demo.

– At 0:35 I add water to dilute the Cu⁺² into the reduction half cell.

– At 1:33 of the video I add Na₂CO_{3 (s)}into the oxidation half cell.

– At 0:35 I add water to dilute the Cu⁺² :

By adding water Cu⁺² ion solution (molarity) decreased and thus the

Voltage Decreased!!!! Explained in terms of LeChateliers Principle and Spontaneity!

Zn⁰ (s) + Cu⁺² —–> Zn⁺² + Cu⁰

^{Stress: decreases}

^{Response: <—————–}^{Shift = voltage drop!}

^{(lowers spontaneity of forward reaction)} The reverse is now favored more than it was which LOWERS the forwards reactions

pathways or spontaneity, which results in lowering the voltage!

__________________________________________________ Lab 2 – The Gerber Voltaic Cell

LAB 2 – Voltaic Cell.pdf View Download

a) Made 2 voltaic cell and identified anode, cathode and tested voltage.

Identified the spontaneous process with positive volts

wrote half reactions, identified ox and red agents.

b) Completed the diagram, conclusion questions, and reviewed errors for the writing of the

conclusion

&nbsp

Conclusion Writing:

1. What did you find or measure Quantitatively? What are the important values of your data? This is normally posted in your results section of a formal writeup. How accurate are you (how close are you to a known standard, E⁰ cell )?

2. Make the leap! = connect your quantitative value and comparison with the known standard in terms of atom/ions or particle to explain a possibly reason for the outcome.

3. Error discussion.

Every laboratory is limited in errors in measurement and human errors. Do not write about these!! Please describe in detail every major limitation of this laboratory and why you believe it may have lead to your outcome. IN this Lab the error discussion will result from things that are NOT FROM YOUR LEAP! Do nor just list errors. I want an explanation how these errors could of resulted in YOUR OUTCOME.

Lab 3 Conclusion review:

1. Please tell me what you measured (voltage) and calculated (percent error). Do not mince words. Get to the point. This is like our results section last year in our formal labs.

2/3: Explain your errors (why your percent error was so low or negative). You will combine the leap with the error analysis here. The leap last year was always about an organism and the leap this year is always about atoms or ions. So what did the atoms or ions do that may have contributed to the large negative error?

There is one error that is the largest and I like to think of it as a love triangle between Mg, Cu⁺² , and H₂O.

This cell was left over night. Notice the Mg electrode is smaller and the cloudy mixture. Were there precipitates?

How did this contribute to the error? Or was this a competing error? Notice some of the precipitates seem to be bluish green, which is an indication that Copper precipitates were also made.

The Standard Reduction Potentials provides clues:

–Error Analysis for the conclusion:

Chemical reactions that may have contributed:

Mg + 2HOH (water) —–> Mg⁺² + 2OH^– + H₂ (g)

Would these ions (Mg⁺² + 2OH^–) form a precipitate with ions already present? The color of the entire battery was bluish? What does that say about movement of Cu⁺² ions?

Would the Cu⁺² ions react with newly formed OH^–? How would LeChatelier’s Principle explain the lowered experimental voltage?

What factors were competing? Based on the experimental voltage which factor dominated?

There are at least 4 errors contributing.. ___________________________________________

Review of the Lab 2 that might help with conclusion:

My video below illustrates the reaction occurring above (the fizzing or production of hydrogen gas).

Time Lapse – Lab 1

Lab 1 – Put all the Voltaic cells in series to run large radio.

______________________________________________________ Jump to: top 9/11 – Weekend Homework: –

1. Complete Question 1 and 2 (AP Question 2002 and 2003)

Intro Voltaic Cells worksheet 1.pdf worksheet –

( They are Past AP problems ) –

Intro Voltaic Cells worksheet 1.pdf
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Intro Voltaic Cells Worksheet 1 key pp.pdf
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2. Review with key posted above or the video posted below.

In question 2 my key does not do a great job in answering some questions..

2a) overall reaction with the greatest voltage:

2Al (s) → 2Al⁺³ (aq) + 3e- 6e- +1.66 volts

3Cu⁺² + 2e– 6e- → 3Cu (s) +0.34 Volts _______________________________________________

2Al (s) + 3Cu⁺² → 2Al⁺³ (aq) + 3Cu (s) E⁰ cell = 2.00 volts

2d) Explain why each salt (ionic compound) is not appropriate:

NaOH –> Although OH^–is soluble and thus produces free ions that will “maintain electrical neutrality” it will cause a precipitate with the Cu⁺² ion in the reduction cell that will lower the reactants causing a shift to the left that would lower the voltage due to Le Chatelier’s Principle

CuS —> This salt is not soluble (large positive and large negative charges) thus their would be NO FREE IONS “to maintain electrical neutrality” and thus this choice of salt in the salt bridge would cause the voltage to remain at zero!

NaNO₃ —-> This salt is soluble and thus will produce free ions “to maintain electrical neutrality” and will facilitate a positive voltage. This salt was weak coulombic attractions due to each of the ions having a low charge density.

3. Please complete the Lab 2 including the conclusion.

Lab 2 is Due Monday, 9/14 in the purple crate in front.

2) Intro Voltaic cell worksheet 1 video: