Zinc gives H2 gas with dil. H2SO4/HCl but not with HNO3 because in HNO3,NO3− ion is reduced and gives NH4+,N2O,NO and NO2 (based upon the concentration of HNO3)
[Zn+2HNO3→Zn(NO3)2+2H]×4 (nearly 6%)
HNO3+8H→NH3+3H2O NH3+HNO3→NH4NO3
4Zn+10HNO3→4Zn(NO3)2+NH4NO3+3H2O
Zn is on the top position of hydrogen in elctro-chemical series.So Zn displaces H2 from dilute H2SO4 and HCl with liberation of H2