CHAPTER 6.1 ACID AND ALKALI

Prepared by cikgu husrita

CHAPTER 6
ACID AND ALKALI

6.1 : PROPERTIES OF ACIDS AND ALKALIS

PROPERTIES OF ACID

• pH value less than 1 - 7
• Tastes sour
• Corrosive
• Turns blue litmus into Red
• React with metals to produce hydrogen gas
• Examples : Hydrochloric acid, Vinegar, lime juice

and etc

6.1 : PROPERTIES OF ACIDS AND ALKALIS

PROPERTIES OF ALKALIS

• pH value more than 7 - 14
• Tastes bitter
• Corrosive
• Turns red litmus into blue
• Does not React with metals
• Examples : soap water, sodium hydroxide solution

• SHOWING THEIR PROPERTIES BY
THE PRESENCE OF WATER.

ACID PROPERTIES ALKALI
Below 7 PH VALUE More than 7
TASTE
Sour Bitter
Yes CORROSIVE Yes
Blue to red LITMUS PAPER Red to blue

React with metal and REACTION WITH No reaction

produce hydrogen gas METAL

Not slippery TASTE OF TOUCH Slippery to the touch 4

ACID

Organic Inorganic

1. Citric acid (Oranges) 1. Hydrochloric 5
2. Malic acid (Apples) acid
3. Lactic acid (Sour milk)
4. Acetic acid (Vinegar) 2. Sulphuric acid
3. Nitric acid

ORGANIC ACID

Acid Source
Acetic acid Vinegar
Lactic acid Fermented milk, yogurt

Formic acid Ant, bee
Malic acid Young apple
Tartaric acid Grapes

Citric acid Oranges, lemon

Tanic acid Tea 6
Carbonic acid Carbonated drink

The role of water in showing the properties of acid’s
and alkali’s

Acid’s and alkali’s only show its properties in the
presence of water
For example when a piece of dry blue litmus paper
is added to solid citric acid, there is no change in
colour
But when the water is added, the litmus paper the
litmus paper turns red

ACIDS AND ALKALIS ONLY SHOWS THEIR
PROPERTIES IN THE PRESENCE OF WATER

ACID AND ALKALI INDICATOR

INDICATOR ACID NEUTRAL ALKALI
Phenolphthalein Colourless Colourless Pink
Universal indicator Blue
Red Green

Methyl orange Red Yellow Yellow
Blue litmus paper Red Blue Blue

Red litmus paper Red Red Blue

• AN INDICATOR IS A COLORING OR MIXTURE OF DIFFERENT COLORINGS THAT CHANGES COLOUR
BASED ON THE SUBSTANCES TESTED.

STRENGTH OF ACIDS AND ALKALIS

pH METER

0

10

pH VALUE

11

APPLICATION OF ACIDS IN DAILY LIFE

Types of Acids Uses
Ascorbic acid To make vitamin C
To produce antiseptics
Boric acid To preserve food and fruits
Benzoic acid In cooking such as making pickle
Tartaric acid
Vinegar Fizzy drink
Tartaric acid Car battery
Carbonic acid
Sulphuric acid

APPLICATION OF ALKALIS IN DAILY
LIFE

Types of Alkali Uses
Magnesium hydroxide To make antacids (milk of
magnesia)
Potassium hydroxide To produce soap
Ammonium hydroxide To make fertilizers

Sodium hydroxide Detergent