Transcript IONIC COMPOUNDS: ACIDS AND BASES

ACIDS AND BASES
Chapter 8 - Honors
Properties of Acids and Bases – Journal 1
• Read and highlight Sections 8.1-8.4 on the worksheet from the
back table. Make vocabulary flashcards for Sections 8.3 & 8.4
• I will be coming around with samples for you to taste. Classify
each of the liquids as an Acid, Base or Neutral based on what
you learn about the characteristics of acids and bases in your
reading.
Acids and Bases
• Acids and Bases are Compounds that have very distinct
properties.
HCl + H2O  H3
1+
O
(aq)
1+Cl
NaOH(s)  Na 1+(aq) + OH 1-(aq)
(aq)
WATER
Before understanding Acids and Bases, you must understand water.
1. It is a polar molecule. Like a magnet.
-
+
-
+
WATER
1. It is a polar molecule. WHY???
Oxygen pulls on the electrons more than Hydrogen does.
Oxygen = Higher ionization energy.
-
+
-
+
WATER
Because water is POLAR (negative side and positive side), what
types of compounds will it DISSOLVE easily?
CHARGED
-
+
-
+
Acids
• Acids: compounds that IONIZE and produce HYDRONIUM IONS
when dissolved in water.
HCl + H20  H3
1+
1O +Cl
• Written also as:
1+
1HCl  H +Cl
Acids
1+
When HCl is put in water, a Hydronium ion, H3O
1+
(hydrogen ion, H ) is formed.
Why might acids be referred to as “PROTON
DONORS”?
Acids: ionization
Acids ARE “PROTON DONORS”
http://www.learning.gov.sk.ca/branches/elearning/tsl/resources/subject_area/science/chem_30_resources/lesson_8/acids_and_bases.shtml
Acids
Characteristics of Acids
1.Taste Sour
2.React Strongly with Metals and
Carbonates (in soil and rocks)
3.Burn skin
4.Conduct electricity in water (electrolyte)
5.Turn blue litmus paper red
Common Acids
Acetic acid
CH3COOH Vinegar
Carbonic acid
H2CO3
Carbonated beverages
Hydrochloric acid
HCI
Digestive juices in stomach
Nitric acid
HNO3
Fertilizer production
Phosphoric acid
H3PO4
Fertilizer production
Sulfuric acid
H2SO4
Car batteries
Bases
• Bases: ionic compounds that DISSOCIATE and produce
HYDROXIDE IONS when dissolved in water.
1+
1• NaOH(s)  Na (aq) + OH (aq)
Bases
http://web.umr.edu/~gbert/ANIMATED/Asoly.HTML
Bases are Ionic
compounds that
break apart
(dissociate) in water
to form a negatively
charged hydroxide
ion (OH 1-).
Why might bases be
referred to as
“PROTON
ACCEPTORS”?
Bases
http://www.learning.gov.sk.ca/branches/elearning/tsl/resources/subject_area/science/chem_30_resources/lesson_8/acids_and_bases.shtml
Bases ARE “PROTON ACCEPTORS”
http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/acm2s2_1.swf
Bases
Characteristics of Bases
1.Taste bitter
2.Feel Slippery
3.Burn your Skin
4.Conduct electricity in water
(electrolyte)
5.Turn red litmus paper blue
Common Bases
Aluminum hydroxide
Al(OH)3
Deodorant, antacid
Calcium hydroxide
Ca(OH)2
Concrete, plaster
Magnesium hydroxide Mg(OH)2
Antacid, laxative
Sodium hydroxide
Drain cleaner, soap production
NaOH
Strength of Acids and Bases
Which would you say is MORE acidic:
• battery acid
• Or milk?
WHY is battery acid MORE ACIDIC?
Strength of Acids and Bases
1. MORE hydronium (H3O 1+) ions.
2. How many hydronium ions are in the strong acid? In
the weak acid?
Strength of Acids and Bases
1. Chemists use a number scale from 0 to 14 to describe
the concentration (amount of) hydronium (H3O 1+) ions
in a solution.
2. This is the pH Scale.
Strength of Acids and Bases
1. The pH of a solution is a measure of the hydronium ion
(H3O 1+) concentration.
Strength of Acids and Bases
1. Neutral substances have a value of 7
2. Their number of hydronium ions equal their number of
hydroxide ions.
Strength of Acids and Bases
1. Distilled water is neutral.
2. It’s hydronium ions equal it’s hydroxide ions
This is because water ionizes slightly.
Strength of Acids and Bases
1.
2.
3.
4.
Acids have a pH value of LESS THAN 7
Bases have a pH value of MORE THAN 7
Which are the strongest acids and bases?
Which are the weakest acids and bases?
5. What is NEUTRAL?
Acids and Bases - JOURNAL
1. Fill in the Identifying Acids and Bases sheet.
Strength of Acids and Bases
What is the difference between the strong and the weak, regardless
of concentration?
Strong substances IONIZE/DISSOCIATE COMPLETELY.
Strength of Acids and Bases
How do you get strong and weak acids and bases?
• STRONG ACIDS/BASES COMPLETELY
IONIZE/DISSOCIATE
• HCl + H2O
H3O + + Cl –
– Reaction only goes in one direction.
•
WEAK ACIDS/BASES DO NOT dissociate/ionize
completely
• NH3 + H2O
NH4+ + OH –
– Reaction goes in both directions. Not all of
the compound ionizes.
–
http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s1/acm2s1_1.htm
pH
1+
H3O
concentration
1+
H3O
concentration
0
1.0
1 x 10
1
0.1
1 x 10
2
0.01
1 x 10
3
0.001
1 x 10
4
0.0001
1 x 10
0
-1
-2
-3
-4
If you multiplied this
number by 100, what
would be your chances
of finding a hydronium
ion in solution?
•100%
-5
If pH is the measure
of hydronium
ions, why are
the lowest numbers?
5
0.00001
1 xacids
10
6
0.000001
1 x 10
7
0.0000001
1 x 10
8
0.00000001
1 x 10
9
0.000000001
1 x 10
10
0.0000000001
1 x 10
11
0.00000000001
1 x 10
12
0.000000000001
1 x 10
13
0.0000000000001
1 x 10
14
0.00000000000001
1 x 10
-6
•10%
-7
•1%
-8
-9
-10
-11
-12
So, your chances get
slimmer as the exponent
gets LARGER.
The fewer the H3O 1+,
the weaker the acid.
-13
-14
http://www.purchon.com/chemistry/acids.htm#animation
Strength of Acids and Bases – Journal
Fill in the Acids and Bases Practice Sheet.
Reactions between Acids and Bases
• When bases REACT with acids, the process is called
NEUTRALIZATION.
Reactions between Acids and Bases
• They react to form a salt and water (& HEAT)
Hydrochloric Acid + Sodium Hydroxide  Water + Table Salt
HCl + NaOH  H2O + NaCl
Common Salts
Sodium chloride
NaCl
Food flavoring, preservative
Sodium carbonate
Na2CO3
Used to make glass
Potassium chloride
KCl
Used as a salt substitute to
reduce dietary intake of sodium
Potassium iodide
Kl
Added to table salt to
prevent iodine deficiency
Magnesium chloride MgCl2
De-icer for roads
Calcium carbonate
CaCO3
Chalk, marble floors, and tables
Ammonium nitrate
NH4NO3
Fertilizer, cold packs
Acids and Bases and Neutralization
•
One of the most important aspects of a
living system is the amount of acidity or
alkalinity
NEUTRALIZATION:
Why do we need to know?
•
•
Control of pH is very
important
Control is
accomplished with
buffers
NEUTRALIZATION:
Why do we need to know?
•
Buffers neutralize
small amounts of
either an acid or
base.
NEUTRALIZATION:
Why do we need to know?
Alkalinity – the ability of a stream to neutralize acids.
Properties of Acids and Bases – Journal 5
• Come in, take out your homework, and get your LAB
sample.
• Write an equation that shows NEUTRALIZATION. Include the names
of the REACTANTS and PRODUCTS.
• What is the range of the pH scale? The range for acids? Bases?
Neutral?
• What is the strongest Acid value? Base value? What would be a
weak acid? Weak base?