7.1 ACIDS AND BASES

NURUL ASHIKIN BT ABD RAHMAN

LEARNING OUTCOME

At the end of this lesson, students are able to: • State the meaning of acid, base and alkali.• State uses of acids, bases and alkalis in daily

life.• Explain the role of water in the formation of

hydrogen ions to show the properties of acids.• Explain the role of water in the formation of

hydroxide ions to show the properties of alkalis.• Describe chemical properties of acids and

alkalis.

Meaning Of Acids, Base And Alkalis

ACID

Chemical compound that

ionises to produce H+ or H3O+ in water.

Ex: HCl H+ + Cl-

Chemical compound that

can neutralise an acid to form salt

and water.

Base + acidsalt + water

Ex: MgO, ZnO, NaOH, KOH

Bases that can dissolve in water to

produces hydroxide ion, OH-

Ex: NaOH (s) Na+ + OH-

BASE ALKALI

H2O H2O

Arrhenius’ definition:

Role of water to shows properties of Acids

The properties of acid is due to the presenceOf hydrogen ions, H+ (aq)

Acid H+

Without water, acid will not behave as anacid.

H2O

Role of water to shows properties of Alkali

The properties of alkali is due to the presenceOf hydroxide ions, OH- .

Alkali OH-

Without water, alkali will not behave as analkali.

H2O

Properties Of Acids And Alkalis

• Sour taste• pH < 7• Turn blue litmus

paper to red• React with bases to

form salt & water

ACID ALKALI

• Bitter taste• pH > 7• Turn red litmus

paper to blue• React with bases to

form salt & water

Chemical Properties Of Acids

ACIDWith metal

With base

With metal carbonates

Salt & Hydrogen gas

Ex: H2SO4 + Zn ZnSO4 +

H2

Salt & water

Ex: HCl + NaOH NaCl +

H2O

Salt, carbon dioxide gas & water

Ex: 2HCl + CaCO3 CaCl2 + CO2 + H2O

Chemical Properties Of Alkalis

ALKALIWith metal

ion

With acid

Heat with ammonium

salt

Metal hydroxide

Ex: Fe3+ + 3OH- Fe(OH)3

(precipitate)

Salt & water

Ex: HCl + NaOH NaCl +

H2O

Ammonia gas, water and salt

Ex: NH4+ + OH- NH3 + H2O

Uses Of Acid

H2SO4

Benzoic acid, ethanoic acid

Carbonic Acid

Nitric Acid, HCl

Use Of Acids In Daily Life

HCl

H2SO4

HCOOH

To clean metals before electroplating.

To make paints, detergents, fertilizers, electrolyte.

To coagulate latex.

Use Of Acids In Daily Life

Benzoic Acid

Ethanoicacid

Carbonic Acid

To preserve food

A component of vinegar

To make carbonated acid

Uses Of Alkali

MgOH: neutralisesacids

NaOH

Al(OH)3, Mg(OH)2 : alkali neutralise excess acid in

our stomach

NH3 solution

Use Of Bases In Daily Life

NH3

NaOH To make soap, detergents.

MgOH

To make Fertilizers, to keep latex in liquid form, as a sink cleaning agent.

To make toothpaste, gastric pills (antacids).

7.1 : ASIDS AND BASESThe following is some information on magnesium hydroxide:

a) What is base?b) How is alkali different from a base?c) State three physical properties of an alkali.d) Write a balanced chemical equation to show the

reaction between hydrochloric acid and magnesium hydroxide.

   

Magnesium hydroxide is one of the ingredients found in toothpaste and potassium hydroxide is used as the

electroyte in alkaline batteries. Magnesium hydroxide is a base and potassium hydroxide is an alkaline.

Answer:

What is base? A base is a substance that react with an acid to form salt

and water only.  How is alkali different from a base? An alkali is a soluble base that forms a solution when

dissolved in water and ionises to produce hydroxide ions.  State three physical properties of an alkali. Alkali is bitter. Slippery. Turn red litmus paper blue.  Write a balanced chemical equation to show the reaction

between hydrochloric acid and magnesium hydroxide. Mg(OH)2 (s) + 2HCl (aq) MgCl2 (aq) + 2H2O (l)

THE END...