The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is :

[Given : The threshold frequency of platinum is 1.3 $$\times$$ 10¹⁵ s^$$-$$1 and h = 6.6 $$\times$$ 10^$$-$$34 J s.]

At 25$$^\circ$$C and 1 atm pressure, the enthalpy of combustion of benzene (I) and acetylene (g) are $$-$$ 3268 kJ mol^$$-$$1 and $$-$$1300 kJ mol^$$-$$1, respectively. The change in enthalpy for the reaction 3 C₂H₂(g) $$\to$$ C₆H₆ (I), is :

Solute A associates in water. When 0.7 g of solute A is dissolved in 42.0 g of water, it depresses the freezing point by 0.2$$^\circ$$C. The percentage association of solute A in water, is :

[Given : Molar mass of A = 93 g mol^$$-$$1. Molal depression constant of water is 1.86 K kg mol^$$-$$1.]

The K_sp for bismuth sulphide (Bi₂S₃) is 1.08 $$\times$$ 10^$$-$$73. The solubility of Bi₂S₃ in mol L^$$-$$1 at 298 K is :