Q8 of 47 Page 1

Arrange the hydrides of group 16 in order of increasing boiling points,giving reason. Name the hydride which is most stablethermodynamically.

The elements of group 16 (from top to bottom) are oxygen (O), sulphur (S), selenium (Se), tellurium (Te) and polonium (Po, radioactive).


Electronegative elements like N,F,O can form intermolecular hydrogen bonding with water to stabilise the molecule.


Due to intermolecular hydrogen bonding, the stability of the molecule increases along with physical properties like boiling point. So, H2O has the highest boiling point.


For the remaining elements, the boiling points are determined by Van-der-Waals forces. These forces are stronger for those which have high molecular mass and surface area, and higher will be their boiling points.


We know, down the group of a periodic table, molecular mass and surface area increases, and for group 16, it is Te>Se>S.


So, their hydrides boiling points are H2Te>H2Se>H2S.


Overall the order stands as : H2O>H2Te>H2Se>H2S.


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Cathode : E° = -2.71V


E° = 0.00 V


Anode : E° = 1.36V


E° = 1.23V


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