In a compound C, H and N atoms are present in 9 : 1 : 3.5 by weight . Molecular weight of the compound is 108 g mol^-1 . Molecular formula of compound is

Number of atoms in 558.5 gram Fe (at. wt. of Fe = 55.85 g mol^-1) is

Uncertainty in position of a minute particle of mass 25 g in space is 10^-5 m. What is the uncertainty in its velocity (in ms^-1) (h = 6.6 $$\times$$ 10^-34 Js)

In a hydrogen atom, if energy of an electron in ground state is -13.6 eV, then that in the 2^nd excited state is