TEST for sulfur experiment help?? ?

Question

*loosely combined sulfur after boilng with sodium hydroxide form sodium sulfide that gives a black precipitate withlead acetate.

To 2 ml of dilute sodium hydroxide in a test tube, add a pinch of dry egg albumin. Heat for a minute or more,cool the test tube in a runing water and add 10 drops of lead acetate.

A. What is the color of the precipitate?_________

B.What compound is responsible for the coloration?____________

C. Give the chemical equation involved in the experiment:

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Answer 1

The lead acetate test is used to determine the presence of sulfur in amino acids.

A.

The precipitate is black.

B.

The product of this reaction is black lead (II) sulfide. It forms upon the reaction between lead (II) acetate and the sulfur in the egg.

C.

dilute sodium hydroxide in test tube:

NaOH ---> Na+  + OH-

addition of dry egg albumin:

2Na+  +  S ---> Na2S ---> 2Na+ + S2-

addition of lead acetate:

S2-  + Pb2+ ---> PbS