Solid Ba(NO₃)₂ is gradually dissolved in a 1.0 $$\times$$ 10^-4 M Na₂CO₃ solution. At what concentration of Ba²⁺ will a precipitate begin to form ?
(K_sp for BaCO₃ = 5.1 $$\times$$ 10⁻⁹ )

On the basis of the following thermochemical data :
($$\Delta _fG^oH^+_{(aq)}$$ = 0)

H₂O(l) $$\to$$ H⁺(aq) + OH^-(aq); $$\Delta H$$ = 57.32 kJ
H₂(g) + $${1 \over 2} O_2(g) \to$$ H₂O(l); $$\Delta H$$ = -286.20 kJ

The value of enthalpy of formation of OH⁻ ion at 25^oC is :

A binary liquid solution is prepared by mixing n-heptane and ethanol. Which one of the following statements is correct regarding the behaviour of the solution ?

Which of the following has an optical isomer ?