Why does the colour of aqueous `NiCl_(2)` solution change at various stages when ethylenediamine is gradually added to it?

Why is the aqueous solution of BeCl_(2) acidic ?

Explain the phenomenon : "When phenolphethaline is added to aqueous solution of Borax the colour of the solution changed to pink which is again turn colourless if glycerol is added to it

Orange colour of Cr_(2)O_(7)^(2-) ion changes to yellow when treated with an alkali, why ?

Why is the aqueous solution of Cu(NO_(3))_(2) acidic?

Which out of Na_2CO_3 solution & NaHCO_3 solution, changes the colour of phenolphthalein into pink?

The dipole moment of a violet solution of iodine in cyclohexane is zero. When benzene, dioxane or pyridine is added to it, its colour changes and the dipole moment of I_(2) in the presence of these solvents becomes 1.8, 3.0 and 4.5D, respectively. Explain.

When lead nitrate solution is added to an aqueous solution of H_2S , a black precipitate is obtained. However, when lead nitrate solution is added to the filtrate obtained by passing the solution of H_2S through activated charcoal, no black precipitate is obtained. Explain these observations.

When mercuric iodide is added to aqueous solution of KI:

State, the equations, what happens when : Excess of ammonia solution is gradually added to a solution of CuSO_(4)