Having a horrible time with my post lab, please help!! Part A - When I added NaO

Question

Having a horrible time with my post lab, please help!!

Part A - When I added NaOH It turned the precipitate from yellow to white. Once HCl was added it changed back to yellow

Part B - When AgNO3 was added the precipatate formed and solution turned clear from orange. When NaCl was added it turned back to orange.

Part C - Initial color was purple. When H2O was added it turned pink. With a hot bath it turned back purple. With a ice bath it went back to pink.

Part D - Mixed bromothymol blue turned from green to orange when HCl was added. With NaOH added it turned green. More NaOH turned it blue.

Attached are the proceedure and questions.

Explanation / Answer

PART-A

a)

observations --> Pb+2 ions and I- will precipitate as PbI(s) which is yellowcolored

b)

when adding Na(OH)2 then you have excess OH- ions

so

Pb+2 ions precipitate to form Pb(OH)2 which is white

c)

adding excess HNO3 will return the solution precipitate's to solids.

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