1. ACIDS AND BASES
E.Q.: How does the pH of a solution allow us to classify a solution as an acid or a base?

2. Acids and Bases
When a substance dissolves in water it makes a solution.
Solutions can be sorted by whether they are: acid, basic (alkali) or neutral.

3. Acids & Bases Bases Acids Taste bitter Taste sour Turns litmus blue
Acids & Bases
Bases
Taste bitter
Turns litmus blue
Neutralizes acids
Bases are made of metals combined with hydroxide ions (OH-)
Ex. NaOH
Produces OH- when dissolved in water
Feel slippery or “soapy”
Are corrosive
Acids
Taste sour
Turns litmus red
Neutralizes bases
Acids are made of one or more H atoms and one negative ion
Ex. HCl
Produces H+ ions when dissolved in water
Are corrosive

4. Acids & Bases can be both….
STRONG vs WEAK
-- completely ionized -- partially ionized
-- strong electrolyte -- weak electrolyte
-- ionic/very polar bonds -- some covalent bonds
Strong Acids: Strong Bases:
HClO4 LiOH
H2SO4 NaOH
HI KOH
HBr Ca(OH)2
HCl Sr(OH)2
HNO3 Ba(OH)2

5. Acids There are many acids present in our everyday lives.
Lemon juice contains citric acid, and vinegar contains acetic acid (also known as ethanoic acid).
Some strong acids are hydrochloric acid, sulphuric acid and nitric acid.
Some weak acids are ethanoic acid, citric acid and carbonic acid.

6. Bases
Alkalis are present in many cleaning substances used in our homes.
Kitchen cleaners are alkaline because they contain ammonia or sodium hydroxide, which attack grease.
Calcium hydroxide and sodium hydroxide are strong alkalis.
The most recognizable and common weak alkali is ammonia.

7. Indicators
Indicators help you find out whether a solution is acidic or not.
They change color in acid or alkaline solutions.
Different indicators change to different colors.

8. Indicators – pH scale

10. Universal Indicator
Universal indicator changes color in acids and alkalis.
ACIDS
ALKALIS
Neutral
Its color shows the strength of an acid or alkali.

11. Universal Indicator – pH Scale

12. Litmus Test
Litmus is an indicator. It changes color in acid and alkaline solutions.
Litmus is red in an acid.
Litmus is blue in an alkali.

13. The pH scale
1 – 6
8 - 14
Alkalis 7
Acids
Neutral

14. pH SCALE

15. pH  Potential of Hydrogen Concentration (measure) of hydrogen ions
0-14
Less than 7  acidic
More than 7  basic
[ ]= Molarity/Concentration 
pH= -log [H+]
[H+]= 10-pH

16. pOH Potential of Hydroxide Concentration of hydroxide ions
pOH = -log [OH-]
[OH-] = 10-pOH 
pH + pOH = 14

17. pH Calculations pH pOH [H+] [OH-] pH = -log[H+] [H+] = 10-pH
[H+] [OH-] = 1.0 x10-14
pOH
[OH-]
pOH = -log[OH-]
[OH-] = 10-pOH

18. Example
What is the pH of a solution if its Molarity is [H+]= 3.0 x 10-5?
What is the hydrogen ion concentration [H+] in a solution with a pH of 3.12?
pH= -log [H+]
[H+] = 10-pH

19. Example
[ ]= Molarity/Concentration
What is the pOH of a solution that has a moles of NaOH in L of solution?
What is the [OH-] of a solution if the pH is 9?
M = moles/ L = [ ]
pOH = -log [OH-]
pH + pOH = 14
[OH-] = 10-pOH

20. Your turn…. 1) pH = 2.6 2) 3.2 x 10-4 M 3) pOH = 0.16 4) 4.0 x 10-9 M
What is the pH of a solution if the [H+] is 2.8 x 10-3?
What is the [H+] of a solution if the pH is 3.5?
What is the pOH of LiOH if you have 0.45 moles in 0.65 L?
What is the [OH-] of a solution if the pH is 5.6?
What is the pH if the [OH-] is 4.5x 10-2?
1) pH = 2.6
2) 3.2 x 10-4 M
3) pOH = 0.16
4) 4.0 x 10-9 M
5) pH = 12.7 = 13

21. Neutralization
Acids and bases (alkalis) react with each other. The alkali cancels out the acid in the reaction. This is called neutralization.
A salt is made.

22. Salts The salt made depends on the acid and alkali used.
The salt contains the metal atom from the alkali, and the non-metal of the acid molecule.
The salts of sulphuric acid are known as sulphates.
The salts of hydrochloric acid are known as chlorides.
The salts of nitric acid are known as nitrates.

23. Examples Mg(OH)2 + HCl  MgCl2 + salt H2O water HBr + Ca(OH)2 
Hydrochloric
Acid
Magnesium
hydroxide
Magnesium
chloride 2
HBr Ca(OH)2 
CaBr2 +
salt 2
H2O
water
Hydrobromic
acid
Calcium
hydroxide
Calcium
Bromide

24. Applications of Neutralization
Insect Stings
Bee stings are acidic
and can be neutralized with
baking soda (bicarbonate of soda).
Wasp stings are alkaline and can be neutralized with vinegar.
Indigestion: Our stomach carries
around hydrochloric acid.
Too much of this leads to indigestion.
To cure indigestion, you can neutralize the excess acid with baking soda or specialized indigestion tablets.

25. Factory Waste: Liquid waste from factories is often acidic
Factory Waste: Liquid waste from factories is often acidic. If it reaches a river it will destroy and kill sea life of many forms. Neutralizing the waste with slaked lime can prevent this.
Soil Treatment: When soils are too acidic (often as a result of acid rain) they can be treated with slaked lime, chalk or quicklime, all alkalis. Plants and crops grow best in neutral soils.