Which of the following compounds contain(s) no covalent bond(s)? KCl, PH₃, O₂, B₂H₆, H₂SO₄

The combustion of benzene(l) gives CO₂(g) and H₂O(l). Given that heat of combustion of benzene at constant volume is –3263.9 kJ mol^–1 at 25^oC; heat of combustion (in kJ mol^–1) of benzene at constant pressure will be :
(R = 8.314 JK^–1 mol^–1)

Which of the following lines correctly show the temperature dependence of equilibrium constant K, for an exothermic reaction?

For 1 molal aqueous solution of the following compounds, which one will show the highest freezing point?