Which of the following statements are correct? (A) Solutions of acids…

Which of the following statements are correct?

(A) Solutions of acids, bases and salts are the examples of electrolytic conductors.
(B) Solutions of cane sugar, glycerin, alcohol are examples of non-electrolytes.
(C) Oxidation takes place at cathode while reduction takes place at anode in an electrolytic cell.
(D) Silicon and germanium are used in semiconductor devices.

Choose the correct answers from the options given below.

Answer & explanation

Correct answer: option 3

The correct answer is Option (3) → (A), (B) and (D) only

Conductors are of two kinds. In metallic (electronic) conductors the current is carried by electrons; in electrolytic conductors it is carried by ions, which are present in molten salts and in solutions of acids, bases and salts. Substances whose solutions contain no ions are non-electrolytes. In every electrochemical cell, galvanic or electrolytic, oxidation takes place at the anode and reduction at the cathode.

(A) Solutions of acids, bases and salts are the examples of electrolytic conductors. — Correct. They dissociate into ions, e.g. \( \ce{NaCl -> Na+ + Cl-} \), and the moving ions carry the current.
(B) Solutions of cane sugar, glycerin, alcohol are examples of non-electrolytes. — Correct. These covalent molecules dissolve without forming ions, so the solutions do not conduct.
(C) Oxidation takes place at cathode while reduction takes place at anode in an electrolytic cell. — Incorrect. The roles are reversed. In the electrolysis of molten NaCl, for example, chloride ions are oxidised at the anode and sodium ions are reduced at the cathode:
\( \displaystyle \text{Anode: } \ce{2Cl- -> Cl2 + 2e-} \qquad \text{Cathode: } \ce{Na+ + e- -> Na} \)
(D) Silicon and germanium are used in semiconductor devices. — Correct. Their conductivity lies between that of metals and insulators and rises sharply on doping, which is the basis of diodes, transistors and solar cells.

Which of the following statements are correct?

Choose the correct answers from the options given below.

Answer & explanation

Correct answer: option 3

The correct answer is Option (3) → (A), (B) and (D) only

(A) Solutions of acids, bases and salts are the examples of electrolytic conductors. — Correct. They dissociate into ions, e.g. \( \ce{NaCl -> Na+ + Cl-} \), and the moving ions carry the current.
(B) Solutions of cane sugar, glycerin, alcohol are examples of non-electrolytes. — Correct. These covalent molecules dissolve without forming ions, so the solutions do not conduct.
(C) Oxidation takes place at cathode while reduction takes place at anode in an electrolytic cell. — Incorrect. The roles are reversed. In the electrolysis of molten NaCl, for example, chloride ions are oxidised at the anode and sodium ions are reduced at the cathode:
\( \displaystyle \text{Anode: } \ce{2Cl- -> Cl2 + 2e-} \qquad \text{Cathode: } \ce{Na+ + e- -> Na} \)
(D) Silicon and germanium are used in semiconductor devices. — Correct. Their conductivity lies between that of metals and insulators and rises sharply on doping, which is the basis of diodes, transistors and solar cells.