If the shortest wavelength in Lyman series of hydrogen atom is A, then the longestwavelength in Paschen series of He⁺ is :

What is the standard reduction potential (E^o) for Fe³⁺ $$ \to $$ Fe ?
Given that :
Fe²⁺ + 2e^$$-$$ $$ \to $$ Fe; $$E_{F{e^{2 + }}/Fe}^o$$ = $$-$$0.47 V
Fe³⁺ + e^$$-$$ $$ \to $$ Fe²⁺; $$E_{F{e^{3 + }}/F{e^{2 + }}}^o$$ = +0.77 V

5 g of Na₂SO₄ was dissolved in x g of H₂O. The change in freezing point was found to be 3.82^oC. If Na₂SO₄ is 81.5% ionised, the value of x

(K_f for water=1.86^oC kg mol⁻¹) is approximately :

(molar mass of S = 32 g mol⁻¹ and that of Na = 23 g mol⁻¹)

Additin of sodium hydroxide solution to a weak acid (HA)results in a buffer of pH 6. If ionition constant of HA is 10^$$-$$5, the ratio of salt to acid concentration in the buffer solution will be :