Acids and Bases Notes

1
Acids and Bases Notes

http//www.nearingzero.net/screen_res/nz065.jpg
2
I. Strength of Acids and Bases

• A. Bases
• Strong Bases metal hydroxides of Group I and
  II metals (except Be) that are soluble in water
  and dissociate (separates into ions) completely
  in dilute aqueous solutions
• Weak Bases a molecular substance that ionizes
  only slightly in water to produce an alkaline
  (basic) solution (ex. NH3)

3
My uncle was a chemist, a chemist he's no more
for what he thought was H 2 O was H 2 S O 4.
(Ha Ha)

• B. Acids
• Strong Acids an acid that ionizes (separates
  into ions) completely or very nearly completely
  in aqueous solutions (will not be on Ka chart).
• Weak Acids an acid that ionizes only slightly
  in dilute aqueous solutions (will be on the Ka
  chart).

4
Why do white bears dissolve in water? Because
they're polar.

• 1. Binary or hydrohalic acids HCl, HBr, and HI
  hydro____ic acid are strong acids. Other
  binary acids are weak acids (HF and H2S).
  Although the H-F bond is very polar, the bond is
  so strong (due to the small F atom) that the acid
  does not completely ionize.

5

• 2. Oxyacids contain a polyatomic ion
• a. strong acids (contain 2 or more oxygen per
  hydrogen)
• HNO3 nitric from nitrate
• H2SO4 - sulfuric from sulfate
• HClO4 - perchloric from perchlorate

6

• b. weak acids (acids with l less oxygen than the
  ic ending
• HNO2 nitrous from nitrite
• H3PO3 - phosphorous from phosphite
• H2SO3 - sulfurous from sulfite
• HClO2 - chlorous from chlorite
• c. weaker acids (acids with hypo ous have
  less oxygen than the ous ending
• HNO - hyponitrous
• H3PO2 - hypophosphorus
• HClO - hypochorous 

7

• d. Organic acids have carboxyl group -COOH -
  usually weak acids
• HC2H3O2 - acetic acid
• C7H5COOH - benzoic acid

8

• II. Characteristics of Acids and Bases (page
  453-458)
• There are multiple definitions for acids and
  bases and I have summarized them all here. Keep
  in mind that there are some exceptions and this
  is just a guide to follow when trying to
  determine if a substance is an acid or a base.

9
Acids Bases

• Usually contain OH (if they dont they produce
  OH in water)

• Usually begin with H (produce H ions in water)

Acid
Base
10
Acids Bases

• Sour taste

• Bitter taste

11
Acids Bases

• Litmus paper turns red

• Litmus paper turns blue

Acid
Base
12
Acids Bases

• pH paper 1-6 or pH meter

• pH paper 8-14 or pH meter

13
Acids Bases

• Phenolphthalein - colorless

• Phenolphthalein turns pink

Acid
Base
Phenolphthalein is an acid/base indicator
14
Acids Bases

• Feels slippery

• Feels like water

15
Acids Bases

• React with metals to produce H2

Do not react with metals to produce H2
16
Acids Bases

• Electrolyte
• pHgt7

• Electrolyte
• pHlt7

17
Acids Bases

• Arrhenius Acid donates (or produces) hydronium
  ions (H3O) in water or hydrogen ions (H) in
  water
• Bronsted-Lowry Acid donates a proton (H) in
  water, H3O has an extra H, if it donated it to
  another molecule it would be H2O (page 467)
• HNO3 H2O ? H NO3- 
• HNO3 H2O ? H3O NO3-  
• HCl H2O ? H Cl-
• HCl H2O ? H3O Cl-
•  

• Arrhenius Base donates (or produces) hydroxide
  ions (OH-) in water
• Bronsted Lowry Base accepts a proton in water,
  OH- needs an extra H if it accepts one from
  another molecule it would be H2O (page 468)
• KOH H2O ? K OH-
• NH3 H2O ? NH4 OH-

18
Acids Bases

• Lewis Base Not all bases contain OH, any atom,
  ion, or molecule that donates an electron pair to
  form a covalent bond it a base

• Lewis Acid Not all acids contain H, any atom,
  ion, or molecule that accepts an electron pair
  from a covalent bond is an acid

Q. What do you do when you find a dead chemist?
A. Barium.

http//www.gis.net/sjp3/ps.html
19
HF H2O ? F -
H3O Acid Base Conjugate
Conjugate Base Acid
Conjugates

• Here HF donated a proton (H) to the water and
  the water accepted the proton (H).
• HF is referred to as the acid and water is
  referred to as the base.
• The fluorine ion, F- is referred to as the
  conjugate base of HF. F- can accept a proton
  (H) to be stable.
• The hydronium ion, H3O is referred to as the
  conjugate acid of water. H3O can donate a
  proton (H) to be stable.

20
Example Determine the acid, base, conjugate
acid, and conjugate base in each of the following
equations

• HCl H2O ? Cl- H3O
  
• Acid Base Conjugate
  Conjugate
•   Base Acid
•  H2SO4 H2O ? HSO4- H3O
• Acid Base Conjugate
  Conjugate
•   Base Acid
•  NH3 H2O ? OH- NH4
• Base Acid Conjugate Base
  Conjugate Acid

21

• 2. What is the conjugate base of the following
  substances?
• H2O ________________
• NH4________________
• HNO2_______________
• HC2H3O2_________________
•  
• 3. What is the conjugate acid of the following
  substances?
• HCO3-__________________
• H2O____________
• HPO42-____________
• NH3___________

22

• 3. WaterWater is a substance that can act as
  an acid or as a base. Autoionization of water
• H2O H2O ? H3O OH-

23
III. pH Scale brackets mean concentration
or Molarity

• The pH scale indicates the hydronium ion
  concentration, H3O or molarity, of a solution.
  (In other words how many H3O ions are in a
  solution. If there are a lot we assume it is an
  acid, if there are very few it is a base.)
• Q How do you make a
• 24-molar solution?
• A Put your artificial teeth
• in water.

24
Where does the pH scale come from?

• pH scale
• -10 1 2 3 4 5 6 7 8 9
  10 11 12 13 1415
• Acidic Basic
• H3O or H
• 1 0.1 0.01 10-3 10-4 10-5 10-6
  10-7 10-8 10-9 10-10 10-11 10-12
  10-13 10-14
• A lot of H3O Not a lot of H3O
• Acidic Basic

25
(No Transcript)
26
pOH Scale

• The pOH scale indicates the hydroxide ion
  concentration, OH- or molarity, of a solution.
  (In other words how many OH- ions are in the
  solution. If there are a lot we assume it is a
  base, if there are very few it is an acid.)

27

• pOH scale
• -10 1 2 3 4 5 6 7 8 9
  10 11 12 13 1415
• Basic Acidic
• OH-
• 1 0.1 0.01 10-3 10-4 10-5 10-6
  10-7 10-8 10-9 10-10 10-11 10-12
  10-13 10-14
• A lot of OH- Not a lot of OH-
• Basic Acidic

28
Example

• Lemon juice (citric acid) pH 2.0, pOH 12.0
• Pure water pH 7.0, pOH 7.0
• Milk of magnesia pH 10.0, pOH 4.0

• The last words of a chemist
• And now for the taste test.
• 2. I wonder if this is hot?
• 3. And now a little bit from this...
• 4. And now shake it a bit.

29

• Ion product constant for water (Kw)
  Kw H30OH- or Kw HOH-
• Because at 25C
• H l.0 X l0-7 M and
• OH- l.0 X l0-7 M
• the Kw 1.0 X l0-14 mol2/L2
• No matter what an aqueous solution contains at
  25C H OH- l.0 x l0-14
• Kw varies with temperature.
• Neutral solution H OH- Acidic
  solution H gt OH- Basic solution
  H lt OH-

30
4. Calculations Involving pH, pOH, H3O, and
OH- of strong Acids and Bases
1st determine which ion will be produced, either
OH or H3O (Acids produce H3O and bases produce
OH-). 2nd use formula to determine pH or pOH.
3rd check to see if answer is reasonable. pH
-log H3O OR pH -log H pOH -log
OH- pOH pH 14 10-pH H3O OR
H 10-pOH OH-
31
Example Problems

• 1.      What is the pH of a 0.001M NaOH solution?
• 1st step Hydroxide will be produced and the
  OH- 0.001M
• 2nd step pOH -log 0.001
• pOH 3.0
• pH 14.0-3.0 11.0

(Significant figures and pH When conuting
significant figures, only count what comes APTER
the decimal in a pH or pOH value. For example
the number of sig figs in a pH of 12.01 is 2, the
number of sig figs in a pH of 12.0 is 1. This is
only for pH and pOH values!!!)
32
Joke
The answer to the problem was "log(1x)". A
student copied the answer from the good student
next to him, but didn't want to make it obvious
that he was cheating, so he changed the answer
slightly, to "timber(1x)."
33

• 2. What is the pH of a 3.4X10-5M HCl solution?
• 3. What is the pH of a solution if the pOH 5?
• 4. What is the pH of a 10 liter KOH solution if
  5.611 grams of KOH were used to prepare the
  solution?
• 5. What is the pOH of a 1.1X10-5M HNO3 solution?
• 6. If the pH of a KOH solution is 10.75, what is
  the molar concentration of the solution? What is
  the pOH? What is the H?

34

• The pH of a strong acid cannot be greater than 7.
  If the acid concentration H3O is less than
  1.0X10-7, the water becomes the important source
  of H3O or H and the pH is 7.00. Just
  remember to check if you answer is reasonable!
• 7.      What is the pH of a 2.5X10-10M HCl
  solution?
•  
•  
• 8.      What is the pH of a 1.0X10-11M HNO3
  solution?