1. Classifying Chemical ____________
COMPOUNDS
Acids, Bases and Salts

2. Classifying Compounds
We already know how to classify compounds based on the type of bond they form.
Ionic: electrons transferred, ions made.(metal + non-metal)
Covalent: electrons shared. (non-metal + non-metal)
We can also classify compounds into many other categories
Acids
Bases
Salts
Organics
Inorganics

3. Today’s Objectives
Be able to distinguish acids and bases by looking at their:
Properties
Chemical formulas
Learn about the pH scale
How it is related to Acids and Bases
Its significance
How we use it
Textbook Chapter 8 pages

4. Acids and Bases Some Common Acids:
Citrus Juice-Orange, Lemon and Lime
Vinegar
Tomatoes
Anything with a SOUR taste.
We often add acids to our foods to improve taste and help us to absorb nutrients.
CAUTION!!!
Many Acids are CORROSIVE which means they can burn your skin.
Never attempt to identify an acid by touch or taste!

5. Acids and Bases Some Common Bases: CAUTION!!! Eggs Baking Soda Soap
Bleach
Anything with a BITTER taste and/or a slippery feel.
CAUTION!!!
Many Bases are CAUSTIC which means they can burn your skin.
Never attempt to identify a base by touch or taste!
***So if we can’t touch or taste compounds how do we know if they are acids or bases?

6. The pH Scale
A number scale for measuring how acidic or basic a solution is.
pH below 7 = acidic pH above 7 = basic pH 7 = neutral

7. What Do the Numbers Mean?
Each decrease of 1 on the pH scale indicates 10X more acidic.
For example, pH 4 is 10x more acidic than pH 5
pH 3 is 1000x more acidic than pH 6
pH ____ is 100x more acidic than pH 5
pH 1 is x more acidic than pH 14 3

8. What is pH really measuring?
The pH of a solution refers to the concentration of its H+ ions.
Remember: CONCENTRATION is the amount of substance (solute) dissolved in a given volume of solution.
Square brackets are used to signify concentration, [H+], [OH–]
High [H+] = low pH, very acidic
High [OH–] = high pH, very basic
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9. More About pH
If a substance has a lot of H+ ions then it has a low pH.
If a substance has a lot of OH- ions then it has a high pH.
If a substance has the same amount of H+ ions as it has OH- ions then it is NEUTRAL.
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11. pH Indicators
The pH of acids and bases cannot be directly determined by sight.
Instead, pH is measured by other chemicals called indicators or by a pH meter that measures the electrical conductivity of the solution.
pH indicators change colour based on the solution they are placed in.

12. pH and Litmus Paper
Litmus is the most common indicator, and is used on litmus paper.
Two colours of litmus paper:
Blue Litmus Paper Red Litmus Paper
pH above 7 (basic) pH above 7 (basic)
(stays blue) (turns blue)
pH = 7 (stays blue) pH =7 (stays red)
pH below 7 (acidic) pH below 7 (acidic)
(turns red) (stays red)
Memory device:
BAR = BLUE ACID  RED

13. Litmus Paper
ACID
BASE

14. pH Probes
A pH meter uses electrical probes to measure how solutions conduct electricity.
We said that acids and bases like to form H+ ions and OH- ions when in solutions and the concentration of these ions will determine a solution’s electrical conductivity.

15. More About ACIDS
Acids readily react with metals to produce hydrogen gas
We can also identify Acids by looking at their chemical formula.
The chemical formula of an acid usually starts with hydrogen (H_).
Acids with a carbon usually have the C written first.
Acids often behave like acids only when dissolved in water and so they often have the subscript (aq)
Acids conduct electricity because they release hydrogen ions, H+(aq)

16. Common Acids HCl(aq) = hydrochloric acid HNO3(aq) = nitric acid
H2SO4 (aq) = Sulphuric acid
CH3COOH(aq) = acetic acid

17. More About Bases
We can also identify Bases by looking at their chemical formula.
The chemical formula of a base usually ends with hydroxide (OH).
Bases release hydroxide ions OH–(aq)
Bases often behave like bases only when dissolved in water and so they often have the subscript (aq)
Don’t readily react with metals

18. Examples of common bases
NaOH(aq) – Sodium Hydroxide
Mg(OH)2(aq) – Magnesium Hydroxide
Ca(OH)2(aq) – Calcium Hydroxide
NH4OH(aq) – Ammonium Hydroxide

19. BASES ACIDS pH less than 7, corrosive pH more than 7, caustic
Litmus turns RED
Litmus turns BLUE
Conduct electricity (when dissolved in water)
Chemical Formula starts with H
Chemical Formula ends with OH
React with metals to produce H2 gas
Do not readily react with metals

20. Review We can classify Acids and Bases based on: Their pH
Their colour change with indicators
Their conductivity
Their chemical formula
Their reactivity

21. What About SALTS? What is a salt???
Salts are ionic compounds formed when acids and bases react.
Salts are also produced when oxides or carbonates react with acids or when metals react with acids.
Table salt, NaCl, is found in sea water, salt lakes or rock deposits.
NaCl is only one kind of salt.
A salt is made up of a positive ion
from a base and a negative ion from
an acid.
Salts are found in many things:
In batteries, explosives and fertilizers
In multivitamins
In many living cells