Solution:
SOLUTION
HI cannot be prepared by the action of conc. H2SO4 on KI because H2SO4 is an oxidising agent and HI is strong reducing agent.
HI reduces sulphuric acid to sulphur dioxide and itself is oxidised to iodine.
KI+H2SO4→KHSO4+HI
H2SO4+2HI→SO2+I2+2H2O
Hence, HI is prepared by heating KI with conc. phosphoric acid. Same is true for the preparation of HBr.