JEE Advanced 2021 · Paper 2

Some standard electrode potentials at 298 K are given below: Pb²⁺/Pb −0.13 V; Ni²⁺/Ni −0.24 V; Cd²⁺/Cd −0.40 V; Fe²⁺/Fe −0.44 V. To a solution containing 0.001 M of X²⁺ and 0.1 M of Y²⁺, the metal rods X and Y are inserted (at 298 K) and connected by a conducting wire. This resulted in dissolution of X. The correct combination(s) of X and Y, respectively, is(are) (Given: Gas constant, R = 8.314 J K⁻¹ mol⁻¹, Faraday constant, F = 96500 C mol⁻¹)

1. ACd and Ni
2. BCd and Fe
3. CNi and Pb
4. DNi and Fe

The pair(s) of complexes wherein both exhibit tetrahedral geometry is(are) (Note: py = pyridine Given: Atomic numbers of Fe, Co, Ni and Cu are 26, 27, 28 and 29, respectively)

1. A[FeCl₄]⁻ and [Fe(CO)₄]²⁻
2. B[Co(CO)₄]⁻ and [CoCl₄]²⁻
3. C[Ni(CO)₄] and [Ni(CN)₄]²⁻
4. D[Cu(py)₄]⁺ and [Cu(CN)₄]³⁻

The correct statement(s) related to oxoacids of phosphorous is(are)

1. AUpon heating, H₃PO₃ undergoes disproportionation reaction to produce H₃PO₄ and PH₃.
2. BWhile H₃PO₃ can act as reducing agent, H₃PO₄ cannot.
3. CH₃PO₃ is a monobasic acid.
4. DThe H atom of P–H bond in H₃PO₃ is not ionizable in water.