This document discusses acids and bases. It defines acids as substances that produce H+ ions in aqueous solution and bases as substances that produce OH- ions. The document describes the pH scale for measuring acidity and alkalinity. It provides examples of the characteristic reactions of acids with metals, bases, and carbonates. It also discusses the importance of controlling acidity in the environment and describes how acids and bases are encountered in everyday life such as in soil, water, and air.

1. Acids & Bases

2. Our Goals for today
 To determine the difference between Acids &
Bases
 To describe the characteristic reactions of acids
with metals, bases (including alkalis) and
carbonates
 To describe and explain the importance of
controlling acidity in the environment (air, water,
and soil)
 To perform an experiment dealing with Acids &
Bases

3. What is the pH scale?
 The pH scale
measures how
acidic
or basic
a solution is.

4. Identifying Acids and Bases
Acidshave a pH from 0-7
Lower pH value indicates a stronger acid.
Bases have a pH from 7-14
Higher pH value indicates a stronger base.

5. Definitions of Acids and Bases
 An acid is a substance that breaks into [H+] ions in
an aqueous solution.
 A Base (alkaline) is a substance that breaks into
[OH–] ions in an aqueous solution.
 Note: aqueous solution is any solution where H2O
is the solvent.

6. Properties of Acids
 Taste sour
 pH < 7
 Acids affect indicators:
 Acids turn blue litmus to red
 Acids turn methyl orange to red
 Acids neutralize bases producing a salt and water
 Acids react with active metals to produce hydrogen
 Acids react with carbonates to produce a salt,
water and CO2
 Proton donors (Proton = H+ = hydrogen ion)

7. The Reactions of Acids
1. With Bases
2. With Alkali
sulphuric acid + copper(II) oxide 
copper(II)
sulphate
+ water
H2SO4 (aq) + CuO (s)  CuSO4 (aq) + H2O (l)
Acid + metal oxide  metal salt + water
sulphuric acid +
magnesium
hydroxide

magnesium
sulphate
+ water
H2SO4 (aq) + Mg(OH)2 (aq)  MgSO4 (aq) + 2 H2O (l)
Acid + metal hydroxide  metal salt + water

8. The Reactions of Acids
3. With Metals
Other examples:
sulphuric acid + magnesium 
magnesium
sulphate
+ hydrogen
H2SO4 (aq) + mg (s)  MgSO4 (aq) + H2 (g)
Acid + metal  metal salt + hydrogen

9. The Reactions of Acids
4. With Carbonates
Other examples:
hydrochloric
acid
+
calcium
carbonate

calcium
chloride
+ water +
carbon
dioxide
2 HCl (aq) + CaCO3 (s)  CaCl2 (aq) + H2O (l) + CO2 (g)
Acid +
metal
carbonate
 metal salt + water +
carbon
dioxide

10. Properties of Bases
 Taste bitter
 pH > 7
 Bases affect indicators:
 Acids turn red litmus to blue
 Acids turn methyl orange to
 Bases neutralize acids producing a salt and water
 Proton acceptors (Proton = H+ = hydrogen ion)
 It feels slippery

11. Neutralization Reaction
 Exothermic: it gives out heat  temp. of sol. ↑
 Neutralization with ammonia
A solution of ammonia in water is alkaline.
NH3 + H20  NH4
+ + OH–
OH– + H+ of acid
 Complete neutralization reaction: use indicator
PHENOLPHTHALEIN
Alkaline Neutral

12. Everyday Life
 Soil: plants will grow best with the pH close to 7.
⁞ Otherwise, we will lack of plant products
(vegetables, fruits, nuts, beans, etc) to eat.
⁞ It disturbs ecosystem of the river.
⁞ Quicklime (calcium oxide), Slaked lime (calcium hydroxide),
limestone (calcium carbonate)
 Water: factory waste. Liquid waste (often acid) reaches rivers.
⁞ It kills fish and other living things.
⁞ It disturbs ecosystem of the river.
⁞ Slaked lime (calcium hydroxide)

13. Everyday Life
 Air: acid rain.
 Waste gases from our daily activities (such as gases from our
electricity, gases from our transportations, burns from the
factory) go into the air.
 Carbon dioxide + water from the rainfall  carbonic acid
CO2 (g) + H2O (l)  H2CO3 (aq)
 Sulphur dioxide and oxides of nitrogen
sulphur dioxide
+ Air + Water
 Sulphuric acid
oxides of nitrogen  Nitric acid

14. Everyday Life
 Air: acid rain.
⁞ It destroys:
 buildings, concrete, cement (calcium carbonate)
 Bridges, iron railings, car bodies
 Plants
⁞ It dissolves aluminium from minerals in rocks and soil.
⁞ It carries it into the river
⁞ < fish
⁞ Slaked lime (calcium hydroxide)

15. Did we Miss something??
 What happens when the pH of a substance is 7?
 Ans: A pH level of 7 indicates a Neutral Substance i.e:
Water!
What else besides water?