Unit 5
Acids, bases and salts
ALKALIS AND BASES
Pages 129-131
Ms. Rabiya Waheed
CLASSROOM RULES
STARTER
https://youtu.be/zYGnq7-_L9w
Students will:
 Identify the alkalis and bases.
 Describe the properties and uses of alkalis
and bases
• bases
• alkali
• neutralization
• antacids
Alkalis
Alkalis are substances that dissolve in water to give solutions with a
pH greater than 7.
The solution contains an excess of hydroxide (OH-) ions.
What will be the color of
alkalis with litmus paper?
Alkalis and bases
The Venn diagram shows relation between
alkalis and bases.
All alkalis are bases but all bases are not alkalis
Alkalis
Alkalis are bases that is soluble in water. Alkalis are
generally used in the laboratory as aqueous solution.
Examples:
 Sodium hydroxide solution (NaOH).
 Potassium hydroxide solution (KOH).
 Calcium hydroxide solution Ca(OH)2 often known
as limewater.
 Ammonium hydroxide solution NH4OH also known
as ammonia solution.
These solutions contain OH- ions, turn
litmus paper blue and have pH greater
than 7
Bases
A base will neutralize an acid, and as a result salt and
water is formed. This is called neutralization reaction.
Alkalis and bases
The alkalis will also neutralize acids as they
belong to the base group with a difference that
they are soluble in water
Q. How are bases different from alkalis?
Students will:
 Identify the alkalis and bases.
 Describe the properties and uses of alkalis
and bases
Properties of alkalis and bases
Bases:
 neutralize acids to give salt and water only
 are the oxides and hydroxides of metals
 are mainly insoluble in water
Alkalis are bases that dissolve in water, and
 feel soapy to skin
 turn litmus blue
 give solutions with a pH greater than 7.
 give solutions that contain OH- ions
Properties of antacids
Antacids are compounds that are used to neutralize
acid digestion and include:
 Magnesium oxide and magnesium hydroxide
 Sodium carbonate and sodium hydrogencarbonate
 Calcium carbonate and magnesium carbonate
Alkalis-Formula and uses
Name
Formula
Strong/weak Where found or used
Sodium
hydroxide
(caustic soda)
NaOH
Strong
In oven cleaners; in making
soap and paper.
Potassium
hydroxide
(caustic potash)
KOH
Strong
In making soft soaps and
biodiesel
Calcium
hydroxide
(limewater)
Ca(OH)2
Strong
To neutralize soil acidity
and acidic gases produced
by power stations; has
limited solubility
Ammonia
solution
(ammonium
hydroxide)
NH3 or
NH4OH
weak
In cleaning fluids in the
home; in making fertilizers.
Bases- Formula and uses
Name
Formula
Where found or used
Calcium oxide
CaO
For neutralizing soil acidity and
industrial waste; in making cement
and concrete
Magnesium oxide
MgO
In antacid indigestion tablets
A solution of calcium hydroxide in water is alkaline.
a. Which one of the pH below is alkaline
pH 3
pH 6
pH7
pH11
b. Which of the following is common name for calcium hydroxide
Cement
limestone
quicklime
slaked lime
c. Some farmers use calcium hydroxide to control soil acidity.
Why is it important to control soil acidity?
d. Calcium hydroxide reacts with hydrochloric acid. State the
name of this type of chemical reaction
e. What are the products formed as a result of this reaction?
A solution of calcium hydroxide in water is alkaline.
a. Which one of the pH below is alkaline
pH 3
pH 6
pH7
pH11
b. Which of the following is common name for calcium hydroxide
Cement
limestone
quicklime
slaked lime
c. Some farmers use calcium hydroxide to control soil acidity. Why is it
important to control soil acidity?
For the growth of plants.
d. Calcium hydroxide reacts with hydrochloric acid. State the name of
this type of chemical reaction
Neutralization reaction
e. What are the products formed as a result of this reaction?
Salt (calcium chloride) and water
Students will:
 Identify the alkalis and bases.
 Describe the properties and uses of alkalis
and bases
Alkalis and bases
Properties of antacids
Properties and uses of
alkalis and bases