Which one of the following hydride of 17th group has the highest melting point
Down the group as the size of the atom increases affinity of hydrogen towards central atom decreases. Therefore
a) X-H bond enthalpy decreases
b) Thermal stability decreases
c) Reducing power increases
d) acidic strength (Ka) increases
e) pKa decreases….HF has positive pKa value,others have negative pKa values.
Down the group as vanderwaal's forces increases
Melting and boiling points increases
Expected BP and MP….HF<HCl<HBr<HI
Due to H-bonding in HF, it has higher BP and MP than expected.
BP trend…...HCl<HBr<HI<HF
MP trend….HCl<HBr<HF<HI