Archive – week 9 – 19-20
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Week of 10/28 – 11/1
Monday 10/28 – period 2/3
1. Test 2 continues
– period 4 –
2. Test 2 continues
Monday 10/28 – Homework
1. Please complete Lab 8 –
a) Complete the 2 chemical reactions and stoichiometry problems to determine the grams of sodium chloride produced.
b) Determine the percent yield of sodium chloride.
c) There is no conclusion for this lab.
End Of Monday..
Tuesday 10/29 – period 2
1. Acid/Base basics (no pun intended…ok maybe)
Demos – magnesium hydroxide, electrolyte
1. Strong Bases – weak bases Table F
Coulombs Law!
2. Acid and base definition introduction
Why acids are dangerous? – what is the action of H+
Why bases are dangerous? – What is the action of OH–
Neutralization reaction – example : OH- from Mg(OH)2
3. Conductivity of metals – mobile electrons
4. Electrolyte definitions – mobile ions
Strong ACids and Bases are strongest electrolytes
Salts that are soluble are electrolytes in (aq) and (l) phases only
Stiochiometry is with Strong Acids or Strong Bases – (completion reactions)
Weak acids/Weak bases do not completely dissociate.
Vinegar (organic acid) weak acid = structure
5. Blah!!!
Milk of Magnesia = Mg(OH)2 Drano = NaOH
Both produce OH- ions but one is dangerous why?
period 3/4
1. Acid/Base Introduction – Demos
1. Strong Bases – weak bases Table F
Coulombs Law!
2. Acid and base definition introduction
Why acids are dangerous? – what is the action of H+
Why bases are dangerous? – What is the action of OH–
Neutralization reaction – example : OH- from Mg(OH)2
3. Conductivity of metals – mobile electrons
4. Electrolyte definitions – mobile ions
Strong ACids and Bases are strongest electrolytes
Salts that are soluble are electrolytes in (aq) and (l) phases only
Stiochiometry is with Strong Acids or Strong Bases – (completion reactions)
Weak acids/Weak bases do not completely dissociate.
Vinegar (organic acid) weak acid = structure
5. Strong Acids – from Halogens – why HF is weak and why HCl, HBr, HI are strong?
Coulombs LAW!!!!
6. Blah!!!!
Demo: Electrolyte, Salts, Acids, and Bases, NOT WATER, NOT SOLID Salts
Demo: Solubility of a non-electrolyte – using an Acid!
Tuesday 10/29 – Homework:
1. Please complete Lab 8
2. Please complete the form below on todays lecture.
I posted today’s lecture (although not from this year) below if you forgot what I discussed today.
I suggest that you review the last 10 minutes or more to complete the form correctly.
Todays period lesson – You have 2 submissions and the form is on auto-grade.
Intro Acid Base Form:
End Tuesday!
Wednesday 10/30 – period 2/3-
a) Completed Demo with what an electrolyte is using examples from form
Note- taking on whiteboard –
1. Complete Acid Base definitions – NOT including ions from salts
2. Weak acid base equilibria, Conjugate Acid, Conjugate Basde
3. strength of acids, Ka – ability of the conjugate base to recreate the acid
– pH probe demo with straw and washing soda
Completed Page 1 of intro packet!
This is the mechanism of how CO2 acts an acid by the the Lewis Definition.
The most complete definition is the Lewis acid base definition because there are acids and bases that DO NOT HAVE protons to donate or possibly accept BUT create acidic conditions or Basic Conditions.
In table K they list CO2 an acid but it had no protons to donate? It is an acid because when we bubble CO2 in water the conditions in water become more acidic.
 CO2 + H2O ——> intermediate ——> H2CO3 H2CO3 + H2O ——> H3O+ + HCO3 -1
CO2 can accept a pair if electrons (JUST LIKE a proton!!!) so the best and most complete definition of acids and bases is the LEWIS acid base definitions! Lewis acids like CO2 are electron acceptors while bases like water in the example are electron donators!!
– period 4
1. Acid/ Base basics continue
a) Completed Demo with what an electrolyte is using examples from form
Note- taking on whiteboard –
– Started page one Acid Base guys of the packet –
b) Acid Base definitions –
Completed Arrhenius and Bronsted-Lowry BUT NOT LEWIS!
c) Weak acid base equilibria –
*Need to add H3O+ as equal partner as H+
Identified Conjugate Acids, Bases and Conjugate Pairs
Wednesday 10/30 – Homework:
PLEASE NOTE WHICH CLASS YOU ARE AND YOUR HOMEWORK BELOW!
Period 2/3:
1. View lecture below (start at 14:40 to 37:50) and Complete Page 2 of the Acid base Intro Packet and review with the key below (after watching the video):
2. NOW complete the third reaction on the Conjugate Acid Base Pairs and Complex ions new.pdf
and review with the key below:
Period 4:
1. Complete first 2 reactions in the of the Conjugate Acid Base Pairs and Complex ions new.pdf worksheet and review with the key posted above.
2. View lecture below (start at 14:40 to 37:50) and Complete Page 2 of the Acid base Intro Packet and review with the key below (after watching the video):
3. NOW complete the third reaction on the Conjugate Acid Base Pairs and Complex ions new.pdf
and review with the key below:
Today’s Lesson sort of : (START at 14:40 for both classes and END at 37:50!)
End Wednesday..
Thursday – 10/31 – period 2 – Happy Halloween 1. Pumpkin Stoichiometry –
C2-2 ion from CaC2 that helped make acetylene today for our pumpkin stiochiometry experiment.
What kind reaction is this?
CaC2 (s) + 2H2O (l) —–> C2H2 (g) + Ca(OH)2  The Arrhenius definition although a good start to defining acids and bases is not complete because we have chemicals that do not have any hydroxide ions in their structure (like NaOH) but will create acidic or basic conditions in water. In the case above, the hydroxide ion (OH–) was produced by the action of the carbide ion (C2-2). So the Bronsted-Lowry definition is a more complete definition because it includes those chemical species that Produce the Basic or Acidic conditions by Accepting a proton or donating a proton.
In the case above the carbide ion (C2-2) ion is the Bronsted-Lowry base (the carbide ion accepted the proton.) and the water is the Bronsted- Lowry acid (because water DONATED A PROTON) (
*Notice that acids must have electron deficient hydrogen to donate protons (H+).
*Notice that Bases must have an ability to accept protons (H+). Having a lone pair of electrons or having a negative charge helps attract the protons!
The result of this acid base reaction is that acetylene C2H2 was produced.
This acetylene is a an organic compound (molecular) that is the fuel in the combustion reaction:
What kind reaction is this?
C2H2 (g) + 5/2O2 (g) —> 2CO2 (g) + H2O (g)
0r
2C2H2 (g) + 5 O2 (g) —> 4CO2 (g) + 2H2O (g)
So if we want the most optimal pumpkin stoichiometry experiment we need
2 C2H2 molecules to 5 O2 molecules!
period 3/4-
1. Pumpkin Stoichiometry
2. Complete page one of the acid/base intro packet by reviewing the acid /base definitions
INCLUDING Lewis Acids. CO2 discussion notes in Wednesday period 2 above.
a) *Need to add H3O+ as equal partner as H+
b) the Carbide ion in calcium carbide is a Brondsted Lowry acid Arrhenius to Bronsted Lowry
PERIOD 2:
PERIOD 4:
Thursday 10/31 night Homework: Please read carefully!!!!
NO Homework Tonight and
PLEASE DO NOT DO ANY STOICHIOMETRY ON YOUR OWN!
End of Thursday!
Friday – 11/1 – period 2/3 –
1. Homework review of page 2 Intro Packet and Conjugate Acid Base Pairs and Complex ions new.pdf
Complex ion acidity!
3. Page 2 of packet review! – Ka!
3. Auto ionization of water – pH, pOH
4. Demo – pH probe demo with straw and washing soda
Pictures of the pool chemicals
copper ions pH probe
4. Indicators – Page 3 and 4 of Packet
period 4 –
1. Homework review of page 2 Intro Packet and Conjugate Acid Base Pairs and Complex ions new.pdf
AND COMPLEX ION acidity!
2. Weak acid base equilibria – Review
b) strength of acids, Ka – ability of the conjugate base to recreate the acid
Breaking Bad – HF – weak acid
pH probe demo with straw and washing soda – Did not get to…
3. Auto ionization of water – pH, pOH
4. Indicators and Table M – Indicators – Page 3 and 4 of Packet
Chemical indicator Presentation: Today’s lesson: pH and Kw
AP Chemistry Classroom setting – actually walks through some calculations:
Today’s Lesson’s – with pH changes and indicators
Screencast that reviews acid/base definitions, Strength of acid/Base and pH problems:
Friday – 11/1 – Weekend Homework
1. Read the Connections Note below.
2 . Please complete the the Acid Base intro Packet:
Please complete the last page of the packet, pH props and Indicators, and review with the key below.
(pH calculations with Strong acid and Bases)
3: Study for a RAT (quiz) on:
A: the acid/base definitions (identify acids and bases)
B: Strength of acids/bases based on Table L
C: Conjugate Acid base pairs recognition
D: Acid / base calculations, page 3 and 4.
END of Week 9!
Todays *Connections– Stoichiometry (mole ratio) continues with Acid/Base Reactions. The connection we need to make is that salts that are soluble and that produce a hydroxide ion (OH–) into an aqueous solution are bases. These are important ions because they can upset the balance of H+ and OH– in water. Remember that these are naturally occurring ions that occur in water. This called auto-ionization of water.
H2O (l) → H+ (aq) + OH– (aq) Kw = 1 x 10-14
Proton Hydroxide
or
H2O (l) + H2O (l) → H3O+ (aq) + OH– (aq) Kw = 1 x 10-14
Hydronium Hydroxide
From 2 reactions above which are really the same you can see ONE H+ or H3O+ for every ONE OH–.
Acids will increase the H+ or the H3O+ concentration above normal* conditions.
Bases will increase the OH– concentration above normal* conditions.
*Normal conditions refer to water that is NEUTRAL : ( H+ or the H3O+ = OH– ) = pH = 7
H2O (l) → H+ (aq) + OH– (aq)
H2O (l) + H2O (l) → H3O+ (aq) + OH– (aq)
Keq = [Products] = Kw = [H+ / H3O+][OH–]
[Reactants]
*We can use H3O+ and H+ interchangeably. I will write H+ going forward but remember I can use H3O+ at any time and it would mean the same thing. (Whether you have a free proton or a a proton held by water does not matter)
Now the value of Kw (equilibrium constant for the auto-ionization of water) equals = Kw = 1 x 10-14
Kw = [H+ ] x [OH–]
1 x 10-14 = [H+] x [OH–]
If one H+ dissociates for every ONE OH– : H2O (l) → H+ (aq) + OH– (aq) then:
1 x 10-14 = [H+] x [OH–]
1 x 10-14 = [1 x 10-7] x [1 x 10-7 ]
As you can see the concentration (molarity, M) of H+ and OH– ARE THE SAME IN PURE WATER!
They must be the same concentration to equal 1 x 10-14 !
Remember when you multiply exponents you add!
*THIS is WATER AT NORMAL CONDITIONS.
Now we use a convention to measure this balance or unbalance of ions in water. It is called pH.
pH = – log (base 10) of the H+ or H3O+ concentration.
Pure water at 4 degrees Celsius the [H+] or [H3O+] = 1 x 10-7
if you put -log (1 x 10-7) in your calculator you will get : pH = 7
So basically pH is a numerical system that measures “stuffs” the entire concentration (small value) into a exponent (base 10) AND MAKES IT positive for Ease
pH = – log [H+]
a)What if the [H+] = 1 x 10-5 ? What is the pH? Is this an acid, basic or neutral solution?
b)What if the [H+] = 0.001 ? What is the pH? Is this an acid, basic or neutral solution?
c)What if we have a [HCl] = 0.1 M What is the pH? Is this an acid, basic or neutral solution?
d)What if we have a [HCl] = 5.6 x 10-6 What is the pH? Is this an acid, basic or neutral solution?
e)What if you have [NaOH] = 0.001 What is the pH? Is this an acid, basic or neutral solution?
e)What if you have [NaOH] = 3.34 x 10-5 What is the pH? Is this an acid, basic or neutral solution?
*Notice the above problems are strong Acids and Base, which means complete dissociation.
answers on bottom of page..
END of Week 9!
Answers for question in notes above. a) pH = 5 Acidic solution (below 7)
b) pH = 3 Acidic solution (below 7)
c) pH = 1 Acidic solution (below 7)
d) pH = 5.25 Acidic solution (below 7)
e) pOH = 3 thus pH = 14 – 3 = pH = 11 Basic solution (above 7 – more OH– than H+)
f) pOH = 4.48 thus pH = 14 – 4.48 = 9.52 Basic solution (above 7 – more OH– than H+)
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