Page 164 - Chemistry ICSE Class X

150 ICSE Chemistry – 10

3. Nature Electrovalent compounds Polar covalent
(e.g. NaCl, NaOH, compounds.
CuSO , etc.)
4
4. Constituent particles In solutions — Ions In solutions — Ions and
molecules.

Acids, Bases and Salts as Electrolytes

Based on the degree of ionisation or dissociation, acids, bases/alkalis and
UCNVU ECP DG ENCUUKſGF CU UVTQPI CPF YGCM GNGEVTQN[VGU #EEQTFKPIN[ VJG
concentration of ions produced will be high or low. Some typical examples
are described in Table 6.2.

Table 6.2 Acids, bases and salts as electrolytes
Strong electrolytes Weak electrolytes
Acids Acids
+
–
+
–
Hydrochloric acid: HCl(aq) o H (aq) + Cl (aq) Acetic acid: CH 3 COOH(aq) U CH 3 COO (aq) + H (aq)
–
+
+
–
Nitric acid: HNO (aq) o H (aq) + NO (aq) Carbonic acid: H CO (aq) U H (aq) + HCO (aq)
3
2
3
3
3
–
+
2–
+
2–
Sulphuric acid: H SO 4 o 2H (aq) + SO (aq) Hydrogencarbonate ion: HCO (aq) U H (aq) + CO (aq)
4
3
2
3
Bases Bases
+
Sodium hydroxide: NaOH(aq) o Na (aq) + OH (aq) Ammonium hydroxide: NH OH(aq) U NH (aq) + OH (aq)
+
–
–
4
4
–
2+
–
+
Potassium hydroxide: KOH(aq) o K (aq) + OH (aq) Magnesium hydroxide: Mg(OH) (aq) U Mg (aq) + 2OH (aq)
2
–
2+
Copper hydroxide: Cu(OH) (aq) U Cu (aq) + 2OH (aq)
2
Salts Salts
+
2+
–
Potassium chloride: KCl(aq) o K (aq) + Cl (aq) Calcium carbonate: CaCO 3 (aq) U Ca (aq) + CO 3 2– (aq)
+
+
–
–
Sodium chloride: NaCl(aq) o Na (aq) + Cl (aq) Ammonium acetate: CH COONH (aq) U NH (aq) + CH COO (aq)
3
3
4
4
Silver nitrate: AgNO (aq) o Ag (aq) + NO (aq)
+
–
3
3
Conduction of Electricity Through Electrolytes
Electrolytes include electrovalent (or ionic) compounds and highly polar
covalent compounds.
Electrovalent compounds consist of ions, whereas polar covalent
compounds consist of atoms bonded together by polar covalent bonds.
ƒ Solid electrovalent compounds and pure polar covalent compounds
do not conduct electricity.
ƒ Molten electrovalent compounds and their solutions conduct
electricity.
ƒ Pure covalent compounds (both nonpolar as well as polar) do not
conduct electricity both in solid or molten liquid states. However, the
solutions of highly polar compounds (such as HCl) in water conduct
electricity.
Why do solid electrolytes (or solid electrovalent
compounds) not conduct electricity
In solid electrolytes (or electrovalent compounds), the oppositely charged
ions i.e., cations and anions are held together by strong coulombic force.
+
–
In sodium chloride, Na and Cl 6JGUG KQPU CTG JGNF KP VJGKT NCVVKEG RQUKVKQPU ſTON[ CPF VJGTGHQTG ECPPQV
ions are held in their positions in move. There are no free electrons also in the structure of these compounds.
the lattice due to strong coulombic Therefore, solid electrolytes (or electrovalent compounds) do not conduct
force between them. electricity.