For coagulation of arsenious sulphate sol, which one of the following salt solution will be most effective ?

The complex that has highest crystal field splitting energy ($$\Delta $$), is :

The pH of rain water, is approximately :

For the reaction, 2A + B $$ \to $$ products, when the concentrations of A and B both were doubled, the rate of the reaction increased from 0.3 mol L^$$-$$1s^$$-$$1 to 2.4 mol L^$$-$$1s^$$-$$1. When the concentration of A alone is doubled, the rate increased from 0.3 mol L^$$-$$1s^$$-$$1 to 0.6 mol L^$$-$$1s^$$-$$1.