K₂Hgl₄ is 40% ionised in aqueous solution. The value of its van't Hoff factor (i) is:

The reaction, MgO(s) + C(s) $$ \to $$ Mg(s) + CO(g), for which $$\Delta $$_rH^o + 491.1 kJ mol^–1 and $$\Delta $$_rS^o = 198.0 JK^–1 mol^–1, is not feasible at 298 K. Temperature above which reaciton will be feasible is :

The de Broglie wavelength ($$\lambda $$) associated with a photoelectron varies with the frequency (v) of the incident radiation as, [v₀ is threshold frequency] :

Match the following items in column I with the corresponding items in column II.

Item I		Item II
(i)	Na2CO3.10H2O	(A)	Portland cement ingredient
(ii)	Mg(HCO3)2	(B)	Castner-Kellner process
(iii)	NaOH	(C)	Solvay process
(iv)	Ca3Al2O6	(D)	Temporary hardness