$$\begin{gathered} \left(\mathrm{i}\right) {\mathrm{H}}_3{\mathrm{PO}}_4\left(\mathrm{aq}\right) \rightleftharpoons {\mathrm{H}}^{+} \left(\mathrm{aq}\right) + {\mathrm{H}}_2{\mathrm{PO}}_4^{-}\left(\mathrm{aq}\right) \\ \left(\mathrm{ii}\right) {\mathrm{H}}_2{\mathrm{PO}}_4^{-}\left(\mathrm{aq}\right) \rightleftharpoons {\mathrm{H}}^{+} \left(\mathrm{aq}\right) + {\mathrm{HPO}}_4^{2-} \left(\mathrm{aq}\right) \\ \left(\mathrm{iii}\right) {\mathrm{HPO}}_4^{2-} \left(\mathrm{aq}\right) \rightleftharpoons {\mathrm{H}}^{+}\left(\mathrm{aq}\right) + {\mathrm{PO}}_4^{3-}\left(\mathrm{aq}\right) \end{gathered}$$

The equilibrium constants for the above reactions at a certain temperature are K₁, K₂ and K₃ respectively. The equilibrium constant for the reaction ${\mathrm{H}}_3{\mathrm{PO}}_4\left(\mathrm{aq}\right) \rightleftharpoons 3{\mathrm{H}}^{+}\left(\mathrm{aq}\right) + {\mathrm{PO}}_4^{3-} \left(\mathrm{aq}\right)$ in terms of K₁, K₂ and K₃ is 

• K₁+ K₂ + K₂

• $\frac{{\mathrm{K}}_1}{{\mathrm{K}}_2+{\mathrm{K}}_3}$

• $\frac{{\mathrm{K}}_3}{{\mathrm{K}}_1{\mathrm{K}}_2}$

• K₁K₂K₃

Which among the following are having diamagnetic property?

(i) B₂    (ii) N₂    (iii)O₂   (iv) C₂

• II, III

• I ,IV

• II, IV

• I, II

The equilibrium constant (K_c) for the following equilibrium $2{\mathrm{SO}}_2\left(\mathrm{g}\right) + {\mathrm{O}}_2\left(\mathrm{g}\right) \rightleftharpoons 2{\mathrm{SO}}_3\left(\mathrm{g}\right)$ at 563 K is 100. At equilibrium, the number of moles of SO₃ in the 10 litre flask is twice the number of moles of SO₂ , then the number of moles of oxygen is

• 0.4

• 0.3

• 0.2

• 0.1

4.

The energy and radius of electron present in second orbit of He⁺ respectively are

• -109 × 10^-18J, 105.8 pm

• -872 × 10^-18 J, 211.6 pm

• -4.36 × 10^-18 J, 52.9 pm

• -2.18 × 10^-18 J, 105.8 pm

Assertion (A): Na⁺ and Mg²⁺ ions are isoelectronic but the ionic radius of Na⁺ is greater than that of Mg²⁺.

Reason (R): The effective nuclear charge of Na⁺ ion is less than that of Mg²⁺ ion.

• Both (A) and (R) are correct but (R) is not the correct explanation of (A)

• Both (A) and (R) are correct and (R) is correct explanation of (A).

• (A) is not correct but (R) is correct.

• (A) is correct but (R) is not correct.

The work functions of Ag, Mg, K and Na respectively in eV are 4.3, 3.7, 2.25, 2.30. When an electromagnetic radiation of wavelength of 300 nm is allowed to fall on these metal surface, the number of metals from which the electrons are ejected is (1eV = 1.6022 × 10^-19 J).

• 4

• 3

• 2

• 5

The Lewis structure for O₃ molecule is given below. The correct formal charges on oxygen atoms labelled 1, 2, 3 are respectively.

• -1, 0, +1

• +1, 0, -1

• +1, -1, 0

• 0, +1, -1

How many millilitres of 20 volume H₂O₂ solution is needed to react completely with 500 mL of acidified 1 N KMnO₄ solution?

• 224

• 280

• 140

• 56

If -239,- 116 and -286 kJ mol^-1 respectively. The enthalpy change for the oxidation of methanol to formaldehyde and water in kJ is

• - 136

• - 173

• 163

• -163

At 27°C in a 10 L flask 4.0 g of an ideal gaseous mixture containing. He (molar mass 4.0 g mol^-1) and Ne (molar mass 20g mol^-1) has a pressure of 1.23 atm. What is the mass 9 of neon ? (R =0.082 L at K^-1 mol^-1).

• 25.2

• 62.5

• 84.2

• 74.2