Page 162 - Chemistry ICSE Class X

6 Electrolysis

Electrolytes and Nonelectrolytes
CONTENTS
What are electrolytes
ͻ ůĞĐƚƌŽůLJƚĞƐ ĂŶĚ ŶŽŶĞůĞĐƚƌŽůLJƚĞƐ
ͻ ĐŝĚƐ͕ ďĂƐĞƐ ĂŶĚ ƐĂůƚƐ ĂƐ All ionic substances and highly polar covalent compounds dissociate or
electrolytes ionise into ions when dissolved in water. The substances which furnish
ͻ ŽŶĚƵĐƟŽŶ ŽĨ ĞůĞĐƚƌŝĐŝƚLJ ƚŚƌŽƵŐŚ ions in aqueous solution or on melting are called electrolytes.
electrolytes
ͻ ^ŽŵĞ ŝŵƉŽƌƚĂŶƚ ƚĞƌŵƐ ƌĞůĂƚĞĚ ƚŽ Electrolytes include acids, bases and salts. Some typical examples of
electrolysis various types of electrolytes are given here:
ͻ Electrolysis ƒ Acids: Sulphuric acid (H SO ), Nitric acid (HNO ), Hydrochloric acid
3
4
2
ͻ ĐƟǀŝƚLJ ƐĞƌŝĞƐ͗ dŚĞ ƌĞůĂƟǀĞ [HCl(aq)], Acetic acid (CH COOH), Phosphoric acid (H PO ), etc.
ƌĞĂĐƟǀŝƟĞƐ ŽĨ ŵĞƚĂůƐ ĂŶĚ ƚŚĞŝƌ 3 3 4
3
ĐĂƟŽŶƐ ƒ Bases: Sodium hydroxide (NaOH), Sodium carbonate (Na CO ),
2
ͻ WƌĞĨĞƌĞŶƟĂů ĚŝƐĐŚĂƌŐĞ ŽĨ ŝŽŶƐ Ăƚ ƚŚĞ Calcium hydroxide [Ca(OH) , limewater], Potassium hydroxide
2
ĞůĞĐƚƌŽĚĞƐ (KOH), etc.
ͻ ^ŽŵĞ ĞdžĂŵƉůĞƐ ŽĨ ĞůĞĐƚƌŽůLJƐŝƐ ƒ Salts: Sodium chloride (NaCl), Calcium chloride (CaCl ), Copper
2
ͻ ƉƉůŝĐĂƟŽŶƐ ŽĨ ĞůĞĐƚƌŽůLJƐŝƐ sulphate (CuSO ), etc.
4
ͻ ůĞĐƚƌŽƉůĂƟŶŐ
What are the characteristics of electrolytes
All electrolytes show the following common characteristics:
ƒ An electrolyte when dissolved in water, or any other polar solvent,
produces ions. These ions are free to move throughout the solution.
The positively charged ion is called a cation, and the negatively
ůů ŝŽŶŝĐ ƐƵďƐƚĂŶĐĞƐ ĂŶĚ ŚŝŐŚůLJ ƉŽůĂƌ charged ion is called an anion.
ĐŽŵƉŽƵŶĚƐ ĂƌĞ ĞůĞĐƚƌŽůLJƚĞƐ͘ ƒ Molten electrolytes and their solutions in water or any polar solvent
conduct electricity.
ƒ The solution of all electrolytes conduct electricity due to the movement
ƐŽůƵƟŽŶ ŽĨ ĂŶ ĞůĞĐƚƌŽůLJƚĞ ŝƐ ĐĂůůĞĚ
ĞůĞĐƚƌŽůLJƟĐ ƐŽůƵƟŽŶ͘ of ions through them.
The conducting power of an electrolytic solution depends upon
Š Nature of the electrolyte
dŚĞ ĞůĞĐƚƌŽůLJƟĐ ĐŽŶĚƵĐƚŽƌƐ ĂƌĞ ĂůƐŽ
ĐĂůůĞĚ ŝŽŶŝĐ ĐŽŶĚƵĐƚŽƌƐ ďĞĐĂƵƐĞ ƚŚĞLJ Š Concentration of the solution
ĐĂƌƌLJ ĞůĞĐƚƌŝĐŝƚLJ ĚƵĞ ƚŽ ƚŚĞ ŵŽǀĞŵĞŶƚ Š Temperature.
ŽĨ ŝŽŶƐ͘
dŚĞ ĞůĞĐƚƌŽůLJƟĐ ;ŝŽŶŝĐͿ ĐŽŶĚƵĐƟŽŶ What are nonelectrolytes
ŝŶĐƌĞĂƐĞƐ ǁŝƚŚ Ă ƌŝƐĞ ŝŶ ƚĞŵƉĞƌĂƚƵƌĞ͘
The compounds which do not conduct electricity both in pure molten state
ƋƵĞŽƵƐ ƐŽůƵƟŽŶƐ ŽĨ ĂĐŝĚƐ͕ ďĂƐĞƐ
ĂŶĚ ŵĂŶLJ ƐĂůƚƐ ĂƌĞ ŝŽŶŝĐ ĐŽŶĚƵĐƚŽƌƐ͘ and in their solutions are called nonelectrolytes.
DŽůƚĞŶ ĞůĞĐƚƌŽůLJƚĞƐ ĂƌĞ ĂůƐŽ ŝŽŶŝĐ ƒ Solutions of nonelectrolytes contain only molecules.
ĐŽŶĚƵĐƚŽƌƐ͘
ƒ Some typical examples of nonelectrolytes are distilled water, alcohol,
sugar, urea, glucose, etc.
How are the electrolytes classified

'NGEVTQN[VGU CTG ENCUUKſGF KP VJG HQNNQYKPI VYQ ECVGIQTKGU
ƒ Strong electrolytes
ƒ Weak electrolytes