[kenny1999]

it is known that when aluminium ion, lead(II) ion as well as zinc ion , when either of them added to NaOH, white precipate will be formed, and when NaOH is in excess, the precipitate will dissolve to form a colourless solution.

But this is not the true if either of these ion added to excess NH3 ammonia solution instead. Why??

To my understanding, ammonia in water will also partially ionize to give OH- hyrdoxide ion, but why it doesn't form precipiate with those ions when ammonia in excess?

Really so hard to understand why excess ammonia can shift the equilibrium to have an abundent supply of hydroxide ion.

Please *delete me*

[Borek]

What is concentration of OH^- in a solution of strong base? In solution of ammonia? Assuming identical concentration of ammonia/strong base - how do the concentrations of OH^- compare?

[kenny1999]

it is known that when aluminium ion, lead(II) ion as well as zinc ion , when either of them added to NaOH, white precipate will be formed, and when NaOH is in excess, the precipitate will dissolve to form a colourless solution.

But this is not the true if either of these ion added to excess NH3 ammonia solution instead. Why??

To my understanding, ammonia in water will also partially ionize to give OH- hyrdoxide ion, but why it doesn't form precipiate with those ions when ammonia in excess?

Really so hard to understand why excess ammonia can shift the equilibrium to have an abundent supply of hydroxide ion.

[DevaDevil]

what is the pK_b value of ammonia? And that of NaOH?
What does this mean for the abundance of OH^- at identical concentrations of these bases?