Warm Up #3, Week 5
1) Calculate the empirical formula of a compound
that is 75% Carbon and 25% hydrogen by mass.
2) Draw the Lewis structure.
3) Predict the molecular shape (VSEPR).
4) Name the following acids/bases:
a) HBr
b) NaOH
c) HNO2
Strong and Weak Acids
• Strong acids ionize completely
•
There are only 6 strong acids: You must
learn them.
•
•
•
•
•
•
H2SO4
HNO3
HClO4
HBr
HI
HCl
Strong and Weak Bases
• A base is strong if it contains a an
alkali metal or alkaline earth metal and
dissociates completely
NaOH
• Ca(OH)2
•
• A base is weak if it contains any other
metal or (NH4)+; dissociates slightly
• Do not confuse the terms “dilute”
and “concentrated” with “weak”
and “strong”
• They do NOT mean the same
thing
• Dilute and concentrated refer to
# moles per liter
• Strong and weak refer to %
ionization
Common Acids and their Uses
• Hydrochloric acid (HCl) in gastric juice
• Sulfuric acid (H2SO4) in car batteries
• Nitric acid (HNO3) in fertilizer & explosives (TNT)
• Carbonic acid in soft drink (H2CO3)
• Uric acid in urine
• Ascorbic acid (Vitamin C) in fruit
• Citric acid in oranges and lemons
• Acetic acid in vinegar
• Tannic acid in tea and wine
• Tartaric acid in grapes
Common Bases and their Uses
• Sodium hydroxide (NaOH) or caustic soda
used to make soap, biodiesel, & more
• Calcium hydroxide [Ca(OH)2] or limewater
• Ammonium hydroxide (NH4OH) or ammonia
water - a household cleaner
• Magnesium hydroxide [Mg(OH)2] or milk of
magnesia – used as an antacid or a laxative
• Aluminum hydroxide [Al(OH)3] is used in
antiperspirants
• Many bleaches, soaps, toothpastes, and
cleaning agents (drain cleaner, oven cleaner,
etc.)
Practice naming these acids:
1. HNO3 __________ 8. hydroselenic acid __________
2. H2SO4 __________ 9. chromous acid ____________
3. HCl(aq) __________ 10. perchloric acid ___________
4. HI(aq) __________
11. hydrofluoric acid __________
5. HClO3 __________ 12. hypochlorous acid ________
6. H2CO3 __________ 13. hydrobromic acid_________
7. HC2H3O2 ________ 14. bromic acid ___________
Robert Boyle
• First to label
substances as acids or
bases
• Acids ---sour,
corrosive to metal,
changed litmus to red
• Bases (alkalis) --slippery, changed
litmus to blue
New definition came 200 years later
• Arrhenius
1890
Brønsted
Lowry
1923
Acid-Base Theories
• Arrhenius Base – a substance that produces
(OH)- ions when in an aqueous solution
• Ex. Mg(OH)2, NaOH
• Arrhenius Acid – a substance that produces H+
(hydrogen) ions or H3O+1 (hydronium) ions when
in an aqueous solution
• Ex: HCl, HNO3, H2SO4
• Hydronium ion is formed when H+1 attaches to
water molecule (terms are interchangeable)
Acid-Base Theories
•
Brønsted - Lowry Acid - hydrogen
ion donor (proton donor)
• Brønsted -Lowry Base – hydrogen
ion acceptor (proton acceptor)
•All Arrenhius acids and
bases are Brønsted-Lowry
acids and bases
•But some substances are
only Brønsted-Lowry acids
and bases
Need reactions to identify BrønstedLowery acids and bases and need to
connect each reactant to its “partner
product”.
Is it donating or accepting from R to
P?
acid
conjugate (partner) base
base
CH3COOH(aq) + H2O (l)

CH3COO-1 (aq)
+
H3O+1 (l)
conjugate (partner) acid
NH3(g)
HCO3-1(aq)
+
H2O(l)  NH4+1(aq)
+ H2O(l)

+
H2CO3(aq)
OH-1 (aq)
+ OH-1(aq)
• Water is amphoteric or amphiprotic---it can
act as either an acid or base depending on
what it does
• NH3(g) + HOH(l)  NH4+1(aq) + OH-1(aq)
acid
• HBr(aq) + HOH (l)  H3O+1(aq) + Br-1(aq)
base
Find the conjugate base or acid:
• Conjugate base of HCO3 -1
• CO3 -2
• Conjugate acid of HCO3 -1
• H2CO3
• Conjugate base of NH3
• NH2-1
• Conjugate acid of NH3
• NH4+1
Neutralization
• The reaction of an acid and a base
that produces a salt and water.
• Acid + Base  Salt + water
• HCl + KOH  KCl + HOH
• Double replacement reaction
Example Neutralization
• H2SO4 + NH4OH 
• H2SO4 + 2NH4OH  2HOH + (NH4)2SO4
• Mg(OH)2 + H2CO3 
• Mg(OH)2 + H2CO3  MgCO3 + 2H2O
pH Scale
• Definition of acidic, basic, & neutral
solutions based on pH
• acidic: if pH is less than 7
• basic: if pH is greater than 7
• neutral: if pH is equal to 7
Acid - Base Indicators
• AKA pH indicators - substances which
change color with pH,
• Ex. Litmus paper, phenolphthalein,
universal Indicator, cabbage juice
bromothymol blue
• Cabbage Juice
• Red---acid
• Blue---base
• Purple---neutral
• Universal Indicator
• pH 2 - pink
pH 4 - Orange
pH 6 - Yellow
pH 8 - Aqua/Blue
pH 10 - Blue
pH 12 - Violet
http://encarta.msn.com/medi
a_1461500642/Universal_In
dicator.html
http://www.seed.slb.
com/en/scictr/lab/foo
d_ph/res.htm
Aqueous Solutions
• Pure water contains equal amounts of
H+ and OH- ions. It is a neutral
solution
• The relative amounts of these ions in
aqueous solutions determine if it is an
acid, base, or neutral
• H2O(l) + H2O(l)  H3O+(aq) + OH-(aq)
In a neutral solution, the hydrogen ion
concentration multiplied by the hydroxide
ion concentration equals 1 x 10-14 M
[H+][OH] = 1 x 10-14 M
1 x 10-7 M x 1 x 10-7 M = 1 x 10-14 M
This is called the Kw of water
Also:
The pH + the pOH = 14
7 + 7 = 14
• Find the [H+] of a solution with a [OH-1]
ion concentration of 2.5 x 10-8 M.
• [H+] x 2.5 x 10-8 M = 1 x 10-14 M
• [H+] = 4 x 10-7 M
• Find the pOH of a solution with a pH of
2.35
• 2.35 + pOH = 14
• pOH = 11.65
pH Scale---formulas
• pH = potential of hydrogen ion
concentration
• pH = -log[H+]
• [H+] = antilog(-pH)
Ex. Determine the pH given the following
and tell whether it's an acid, base, or
neutral.
• [H+]=1x10-4 M
• [H+]=1x10-13 M
Significant digits in pH
• When rounding for significant digits in
pH answers, the pH has as many
places past the decimal point as the
number of significant digits in the
concentration.
• When rounding for concentration
calculated from pH, the number of
significant digits is the number of
decimal places in the pH.
pH calculations
for strong acids the molarity is the concentration of
the hydrogen or hydronium ion
•
•
•
•
•
•
•
0.0015 M HCl
5.0 x 10-9 M HNO3
1.0 M HClO4
3.27 x 10-4 M HCl
1.00 x 10-3 M HBr
0.00010 M HI
2.0 M HClO4
• 2.82
• 8.30
• 0.00
• 3.485
• 3.000
• 4.00
• -0.30
Calculating [H+]
• pH = 5.63
• 2.3 x10-6 M
• pH = 8.92
• 1.2 x 10-9 M
• pH = 11.93
• 1.2 x 10-12 M
• pH = 3.22
• 6.0 x 10-4 M
• pH =9.00
• 1.0 x 10-9 M
pOH
• pOH is based on the concentration of hydroxide ion.
• pOH = -log[OH-1]
• [OH-] = 2nd log(-pOH)
• pH + pOH = 14
• [H+1][OH-1] = 1x 10-14
pOH calculations
• 0.25 M NaOH
• 1.50 M KOH
• pOH = 0.75
• 0.25 M Ca(OH)2
pOH =
pOH =
[OH-1] =
pOH =
• 0.60
• -0.176
• 0.18 M
• 0.30