IIT JEE 2009 Chemistry Paper2 Code 1 Solutions

8.     Among the following, the state function(s) is(are)

        (A)    Internal energy

        (B)    Irreversible expansion work

        (C)    Reversible expansion work

        (D)    Molar enthalpy

Sol.   (A, D).

 Internal energy and molar enthalpy depends only on initial and final states.They don't depend on the intermediate path.Hence they are state functions.

9.     For the reduction of NO₃^- ion in an aqueous solution, E⁰ is +0.96 V. Values of E⁰ for some metal ions are given below

        V²⁺ (aq) + 2e^- --> V              E⁰ = -1.19 V

        Fe³⁺ (aq) + 3e^- --> E             E⁰ = -0.04 V

        Au³⁺ (aq) + 3e^- --> Au           E⁰ = +1.40 V

        Hg²⁺ (aq) + 2e^- --> Hg           E⁰ = +0.86 V

        The pair(s) of metals that is(are) oxidized by NO₃^- in aqueous solution is(are)

        (A)    V and Hg

        (B)    Hg and Fe

        (C)    Fe and Au

        (D)    Fe and V

Sol.   (A, B, D)

       E_NO3^- (aq)^o =   0.96 V. All V, Fe, Hg have lesser standard reduction potential

        (SRP)                  w.r.t. NO₃^-.

        So, V, Fe, Hg can be oxidized by NO₃^- in aqueous solution.