Acid Base Chemistry Spring 2015. Agenda 5/12/15 Go Over Tests ▫Retakes Intro to Acid-Base Chemistry Red Cabbage Lab Notes: Acids and Bases.

Acid Base ChemistrySpring 2015

Agenda 5/12/15

•Go Over Tests▫Retakes

•Intro to Acid-Base Chemistry

•Red Cabbage Lab

•Notes: Acids and Bases

AcidsWhat is an acid?

– Compounds that produce H+ ions when dissolved in aqueous solution• Arrhenius Model Acid (Original Definition)

Example: HCl(aq) + H20 → H+ (aq)+ Cl-(aq)

• Classified by number of H+ ions that are able to be produced

• Monoprotic– 1 H+ • Diprotic– 2 H+

Example: H2SO4 (aq) → 2H+ (aq) + SO42-

(aq)

• Triprotic-- 3 H+

Example: H3PO4(aq) →3H+(aq) + PO4

3-(aq)

Acids

Properties of Acids:– Litmus Paper—Changed blue to red– Sour/tart tasting– Conducts electricity– React with metals– React with bases– Any other properties from lab?– What common household products fall into

Acid category?

Base

What is a base?▫Any compound that contains OH- and that

produce OH- when dissolved in aqueous solutions Arrhenius Model Base (Original Definition)

▫OH- is called the hydroxide ionExample:

NaOH(aq) → Na+ (aq) + OH-

(aq)

NH4OH(aq) → NH4+

(aq) + OH-(aq)

Bases

Properties of Bases:– Bitter Tasting– Slippery Feeling– Conduct Electricity– React with acids– Litmus paper=turns red paper blue– Any other properties from lab?– What common household products fall into

base category?

Agenda 5/13/15

•Acid-Base Warm up

•Collect Red Cabbage Lab

•Notes: Acid-Base definition and Water

•HW: Complete A-B Intro Assignment

Warm-Up

•Use the data to determine the complete rate law

Rate = .041/M2 *s [A]2 [B]

Any questions about the lab?

Warm-Up

•Acid or Base?▫NaOH▫HCl▫KOH▫H2SO4

▫NH3

Warm-Up

•Acid or Base?▫NaOH -Base▫HCl - Acid▫KOH - Base▫H2SO4 – Acid (diprotic)

▫NH3 - ??? W.T. Heck??

Bronsted Definition (Definition 2)

• Observations of H+ and OH- led to alternate definition of acids and bases known as Bronsted Base and Bronsted Acid– Bronsted Acid: Hydrogen Ion Donor– Bronsted Base: Hydrogen Ion Acceptor

Example: H20 + NH3 → NH4

+ + OH-

• NH4+ now has 4 H+ instead of 3 H+, so it gained H+

• H+ lost by H20, becomes OH-

• H2O considered Bronsted Acid because it donated the H+

• NH3 considered Bronsted Base because it accepted the H+

Water is…•What is water? Is it an acid or base?

▫It depends on what it is reacting with

•If H2O reacts with a base…it’s an acid▫H2O would lose an H+

▫Ex: H2O + HCO3- ↔ H2CO3

+ OH-`

•If H2O reacts with an acid…it’s a base▫H2O would gain an H+

▫Ex: H2O + HCO3- ↔ CO3

-2 + H3O+

Agenda 5/15/15

•Acid-Rain Review

•Discuss pH•Notes: pH

•Notes: Naming Acids/Bases•Practice: Naming Acids/Bases

Acid Rain

•With your partners:

▫What acid(s) make acid rain?▫Why is acid rain so dangerous?▫What are some innovation we have made to

prevent acid rain?

pH

•What did you learn about pH?▫Range?▫Scale?

•Did you learn about pOH?

pH Scale• pH scale from 0-14

▫pH values greater than 7, basic

▫pH values less than 7, acidic

▫pH values equal to 7, neutral

• pH = -log [H+]▫To obtain pH of

substance, must take the negative log of the [H+]

Example: Given: [H+] = 1.0 x 10-3 M All you have to do is plug into pH = -log

[H+]pH = -log (1.0 x 10-3 )pH = 3

Is this acidic, basic, or neutral?What if given [OH-]?•Same process, just use pOH = -log [OH-]Example: [OH-] = 3.4 x 10-3 M pOH = -log (3.4 x 10-3 ) pOH = 2.46

•Once we know either the pH or pOH of a substance, we can calculate the otherpH + pOH = 14

Example:The pH of a sample of rain in an area with

severe air pollution is 3.5. What is the pOH of the rainwater?

All you have to do is plug 3.5 into pH… pH + pOH = 14

3.5 + pOH = 14 pOH = 10.5

•Can also convert from pH or pOH to [H+] or [OH-]▫Just have to use pH = -log [H+] and solve for

[H+]Example:Given : pH = 1.7, find [H+].Step 1: -pH = -1.7 (always make pH negative)Step 2: Plug into your calculator, using

inverse log button : 10-1.7 Answer: 2.0 x 10-2 M

Let’s Check how you did

•Using your assignment from yesterday:

▫Review your answers.▫Should any answer be negative?▫Should any answer be greater that 14?▫Did you solve for [OH-]

Agenda 5/18/15

•Review Acid-Base so far..▫pH/pOH▫Definition of Acids and Bases

•Notes: Naming Acids/Bases•Practice: Naming Acids/Bases

▫White Board practice

•HW: Naming A/B WS

Acid or Base?

•Proton donor•Proton acceptor•Turns red cabbage blue•Turns red cabbage pink•pH lower than 7•pH above 7•Reacts with metals•Feels slippery on your skin

Acid or Base?

•Proton donor ACID•Proton acceptor BASE•Turns red cabbage blue BASE•Turns red cabbage pink ACID•pH lower than 7 ACID•pH above 7 BASE•Reacts with metals ACID•Feels slippery on your skin BASE

pH problem

•If a solution contains 1.0 x 10-2 M of H+ what is the pOH of this solution?

•Answer: pOH = 12

Essential question

•How can I name either an acid or a base?

How do I name bases?• NaOH

▫ Sodium Hydroxide• Ca(OH)2

▫ Calcium hydroxide• LiOH

▫ Lithium Hydroxide

• Come up with rules with your neighbors

Nomenclature•Bases

▫Already know how to do!▫Name of cation, followed by hydroxide

ExampleSodium Na+ = NaOH = Sodium HydroxideCalcium Ca+2 = Ca(OH)2 = Calcium Hydroxide

Magnesium Mg+2 = Mg(OH)2 = Magnesium Hydroxide

How do I name acids?• Come up with rules with

your neighbors. • HCl

▫ Hydrochloric Acid• HF

▫ Hydrofluoric Acid• H2 SO4

▫ Sulfuric Acid• H3 PO4

▫ Phosphoric Acid• HClO

▫ Hypochlorous Acid

Nomenclature

•Binary Acids (H+ and monoatomic)▫Anything ending with “-ide”▫Remove the “-ide” and replace with “-ic”▫Rule: hydro (stem) ic acid

•Examples:▫Chloride

Cl- = HCl = hydrochloric acid▫ Sulfide S-2 = H2S = hydrosulfuric acid

Nomenclature

Ternary Acids :(H+ and polyatomic anion)

• Anions ending with “-ate”, “-ite”

Rule: name of polyatomic , drop

“–ate”, and add “–ic” name of polyatomic, drop

“-ite”, and add “-ous”

Examples:NitrateNO3

- = HNO3 = nitric acid

NitriteNO2

- = HNO2 = nitrous acid

AcetateC2H3O2

- = HC2H3O2 = acetic acid

Hypochlorite ClO- = HClO = hypochlorous

acid

Agenda 5/19

•Stoich Warm-Up

•Review Naming Acids/Bases HW▫HW Quiz

•Household Chemicals Lab

•HW: Finish HH Chemicals Lab

Stoich

2HCl(aq) + 1Mg (s) 1MgCl2 (aq) + 2H+

(aq)

Given 6.00 grams of Mg(s) and 20.0 grams of HCl(aq) which of these chemicals is the limiting reactant?

Let’s Check our HW

Household Chemical Lab

•Obtain 12 different chemicals (1 at a time)•Use at least two different methods of

indicator to determine pH.•May have to use more to determine pH

accurately.•Goggles must be worn because some of

these chemicals can be harmful.

What is it?

•Turns red cabbage blue.

•Turns red litmus paper blue.

What is it?

•Turns blue paper red

•Turns red cabbage pink

What is it?

•Does not affect blue paper

•Turns PhTh pink

What is it?

•Does not affect red paper

•No color change in PhTh

What is it?

•Does not affect PhTh

•Turns blue paper red

What is it?

•Purple in red cabbage•Does not change PhTh color

What is it?

•Green in red cabbage •Does not affect blue litmus paper

What is it?

•Does not change PhTh

•Does not affect blue litmus paper

Agenda 5/20

•Collect Household A/B Lab

•Notes: Kw

•Notes: Strong v. Weak Acid/Base

•Demo: Light Demo

•HW: TBA

What makes an acid strong/weak?•Are all strong acids dangerous?

•Are all weak acids/bases safe?

Strong and Weak Acids and BasesConcentrated/Dilute

• What does it mean for a solution to be concentrated?▫ A large amount of solute▫ High Molarity▫ More chemical, less

water• What does it mean for a

solution to be dilute?▫ A small amount of

solute▫ Low Molarity▫ Less chemical, more

water

Strong/Weak

• Strong Acid/Base▫ Ionizes completely in

water (every molecule ionizes)

▫ Completely dissolves HCl + H20 → H30+ + Cl-

• Weak Acid/Base

▫ Ionizes only slightly (many molecules do not ionize)

▫ Does not completely dissolve

HF + H20 → H30+ + F-

Strong/Weak Acids

Strong Acid Weak Acid

Strong Acids and Bases

•Strong Acids:▫HCl, HBr, HI, HNO3, H2SO4, HClO4

▫Can assume [H+]= [acid] because it completely dissociates

•Strong Bases:▫LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2,

Ba(OH)2

▫Assume [OH-] = [base] because it completely dissociates

•All other acids and bases are weak!!

Weak Acids

•Acid Dissociation Constant (Ka)▫A measure of how strong or weak an acid is.▫Expressed using equilibrium constant

(remember those?!?!) HX(aq) + H20(l) H30+

(aq) + X- (aq)

Ka= [H30+ ] [X-]

[HX] OR

HX(aq) H+(aq) + X-

(aq)

Ka = [H+] [ X-]

[HX]

The larger the value of Ka, the stronger the acid!

Weak Acids

•Example: HClO2(aq) ↔ H+

(aq) + CHO2-(aq)

Ka = [H+] [CHO2- ]

[HClO2]

Ka = 1.8 x 10-4

If a different acid, HC2H3O2, is found to have

Ka= 1.8 x 10-5, which is the stronger acid?

Weak Bases•Weak Base + Water ↔ (conjugate acid) +

OH-Example: H20(l) + NH3 ↔ NH4

+ + OH-

•Base Dissociation Constant (Kb)▫Ratio of conjugate acid and OH- to weak baseExample (from above):

Kb= [NH4+] [OH-]

[NH3]

Strong/Weak Acid TestsSolution Reaction Lite Brightness

1 Distilled H2O

2 1 M HCl

3 1 M NaOH

4 1 M HC2H3O2

Keq for water is…?• Keq = [H+][OH- ]

• Keq always equals 1.0 x 10-

14

• If [H+ ] = [OH- ] then substance is neutral

• [H+] > [OH-] is an acidic solution

• [H+] < [OH-] is a basic solution

Example:Determine if the following is an acid, base, or neutral

substance: [H+]= 4 x 10-11 M

We know that Kw= [H+] [OH-] = 1.0 x 10-14

So, all we have to do is substitute in known concentration…

[4 x 10-11M][OH-] = 1.0 x 10-14

[OH-] = 2.5 x 10-4 M

Answer: Base.

Agenda 5/20

•pH Warm-Up

•Notes: Kw

•Practice: Kw

•Notes: Titration•Practice: Titration

•Demo: Titration Lab for Friday

pH and pOH

•There is a solution of .15M HCl. What is the [OH-] of this solution?

•Ans: [OH-] = 6.7 x 10-14 M•Well that was not very fun..

Keq for water is…Kw

• KW = [H+][OH- ]

• KW always equals 1.0 x 10-

14

• If [H+ ] = [OH- ] then substance is neutral

• [H+] > [OH-] is an acidic solution

• [H+] < [OH-] is a basic solution

Example:Determine if the following is an acid, base, or neutral

substance: [H+]= 4 x 10-11 M

We know that Kw= [H+] [OH-] = 1.0 x 10-14

So, all we have to do is substitute in known concentration…

[4 x 10-11M][OH-] = 1.0 x 10-14

[OH-] = 2.5 x 10-4 M

Answer: Base.

Let’s Practice this

•Finish this practice in your seats.

•I will collect it in 10 minutes.

Highway Tragedy

•http://www.wtsp.com/video/1581292146001/1/1000-gallons-of-sulfuric-acid-spill-on-Highway

Neutralization!

A truck spills 80,000 liters of 3.0 M sulfuric acid on the highway. A 6.0 M solution of sodium hydroxide will be used to “clean up” the spill. How many liters of NaOH will be needed for the job?

H2SO4 + 2 NaOH Na2SO4 + 2 H2O

• Hint: this is a stoich problem!!• How many moles of H2 SO4 ?• How many moles of NaOH do you need?• How many liters of NaOH is that?

•Neutralization Reaction▫An acid and a base react to produce H20 and

a salt

Example:HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

If given the reactants can you determine the products? (don’t forget to balance!)

Try: HNO3(aq) + Mg(OH)2(aq)

Answer: 2HNO3(aq) + Mg(OH)2(aq) → Mg(NO3)2(aq) + 2H20(l)

Titrations!

Titration is a process that allows us to determine the concentration of an unknown solution.

Standard Solution – Solution of known concentration

Unknown Solution – Solution where concentration is not known

Endpoint – Point at which perfect neutralization has been reached

Indicator – Substance used to “reveal” the endpoint

Back-titrating – If we miss the endpoint, we can back-titrate by adding more of the unknown solution

Titration•How can you tell when end point has been

reached?▫Indicator changes color▫For strong acid-strong base titration, pH = 7▫When neutralized : mol H+ = mole OH-

Titration Calculations

•When neutralized, mol H+ = mol OH-▫MAVA=MBVB

▫Looks just like our dilution equation!!

•Note: When not 1 H+ or 1 OH-, must multiply concentration of acid or base for M by #

•Example:H2SO4 has 2Hs so it takes twice as much

NaOH to neutralize it!!

Agenda 5/22/15

•Titration Lab

•You must collect all data today!!

•We can finish writing up lab on Monday!

Titration Lab• You must use the same Base the entire time!

• Part 1: Two trials to determine [NaOH]▫ 10ml acid in flask ▫ 2 drops phth ▫ Drops of base until LIGHT PINK, NOT DARK PINK

• Part 2: Two trials to determine [HCl]▫ .50 grams of unknown in 50 mL distilled water▫ 2 drops phth in with acid▫ Drops of base until LIGHT PINK, NOT DARK PINK

• DO NOT FORGET TO ADD THE PhTH▫ Please add this to the flask, not the buret!!

• Make a data table on the back of your lab

Data Table ExamplePart 1 Initial HCl Final HCl Initial

NaOHFinal NaOH

Trial 1

Trial 2

Part 2 Initial NaOH

Final NaOH

Calculated [NaOH]:________

Trial 1 Calculated moles of NaOH

_________

Trial 2 Calculated moles _________of NaOH

Agenda 5/26/15

• Titration Warm-Up

• Recap Lab from Friday▫Complete Lab and Data Table

• Titration Practice Problems

• Review Acid/Base Chemistry for Test tomorrow

• HW: Study for Test Tomorrow!!

Data Table Part IPart 1 Initial HCl Final HCl Initial

NaOHFinal NaOH

Trial 1 0.00 10.50 0.00 9.80

Trial 2 10.50 11.10 9.80 19.00

Part 2 Initial NaOH

Final NaOH

Calculated [NaOH]: ????????

Trial 1 Calculated moles of NaOH

_________

Trial 2 Calculated moles _________of NaOH

Data Table Part IIPart 1 Initial HCl Final HCl Initial

NaOHFinal NaOH

Trial 1 0.00 10.50 0.00 9.80

Trial 2 10.50 11.10 9.80 19.00

Part 2 Initial NaOH

Final NaOH

Calculated [NaOH]: ????????

Trial 1 0.00 14.60 Calculated moles of NaOH

_________

Trial 2 14.60 30.00 Calculated moles _________of NaOH

Hints for Calculations

•Remember:▫MaVa = MbVb

▫Neutralization occurs when moles acid = moles base

▫Molar Mass: # of moles / gram of chemical