Q7 of 26 Page 1

Define fuel cell and write its one advantage.

Fuel cells are galvanic cells which convert heat liberated during burning of H2, methane, methanol direct into electricity. E.g. H2-O2 fuel cell.


In this cell, H2 gas through anode and O2 gas through cathode is bubbled into aq. NaOH solution through carbon electrode.


The electrode reactions are as follows-



Its advantages are - it is highly efficient (70%), pollution free and the biproduct is water.


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5

C-O bond is much shorter in phenol than in ethanol. Why?

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Why does a solution containing non-volatile solute have higher boiling point than pure solvent? Why is elevation of boiling point a colligative property?

 8

Account for the following:

(a) The 2 oxygen- oxygen bond lengths in ozone molecule are identical.


(b) PbCl4 is more covalent than PbCl2.


OR


Xenon does not form fluorides such as XeF3 and XeF5. Why?


 9

What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its important use.