Electrochemistry

AIPMT 2001MCQEasy📈 Topic in 12% papers+4−1

Ques. 1AIPMT 2001

The most convenient method to protect the bottom of ship made of iron is

coating it with red lead oxide
white tin plating
connecting it with Mg block
connecting it with Pb block

Answer

(3) connecting it with Mg block

Solution

As per NCERT, corrosion of iron can be prevented by sacrificial protection: iron is covered with or connected to a more active metal (such as Mg or Zn), which is oxidised in preference to iron.

Since E Mg2+/Mg = -2.37 V is far more negative than E Fe2+/Fe = -0.44 V, a magnesium block connected to the hull corrodes instead of the iron, and it is easily replaced.

Tin and lead, on the other hand, are less active than iron, so once their coating or contact is broken iron corrodes even faster; a paint layer of red lead also wears off in sea water.

The most convenient method is connecting the ship's bottom with an Mg block.

Answer: (3)

Keep practising — Electrochemistry

Ques. 2AIPMT 2000

Cell reaction is spontaneous when

is negative
is positive
E red is positive
E red is negative

Ques. 3AIPMT 2000

Ionic conductances of Ba2+ and Cl- ions at infinite dilution are 127 and 76 ohm-1 cm2 mol-1 respectively. Equivalent conductance of BaCl2 at infinite dilution is

139.5
101.5
203
279

Ques. 4AIPMT 2000

For the disproportionation of copper 2Cu+ Cu2+ + Cu, E is (Given E for Cu2+/Cu is 0.34 V and E for Cu2+/Cu+ is 0.15 V.)

0.49 V
-0.19 V
0.38 V
-0.38 V

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