In the experiment of establishing the relative reactivity of Halogens and Halide
ID: 832219 • Letter: I
Question
In the experiment of establishing the relative reactivity of Halogens and Halide Ions a student performed the following two tests on an unknown solution containing one halide ion. When he added Cl2(aq) and CH2CL2 to a sample of the unknown sloution, he observed a dark color in the CH2CL2 layer. When he added 0.1M AgNO3 to another sample of the unknown , a light yellow precipitate formed. The sloution remained cloudy after he added concentrated NH3(aq).
(a) What information was revealed by each test?
(b) What halide was present in the unknown?
(c) What test would you perform to confirm the accuracy of your identification in (b)? What would you observe as a result of th etest , if your identification were correct?
Explanation / Answer
both iodide & bromide give yellow ppts with silver
AgI is a definite bright yello
AgBr is a light off white yellow
on adding Cl2 to bromide, it produces a light orange solution in the organic layer
on adding Cl2 to iodide, it produces an extremely dark purple solution in the organic layer
neither AgBr or AgI will dissociate very well in concentrated ammonia
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(a.) What information was revealed by the test?
(b.) What halide ion was present in the unknown?
i feel that you have iodide
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c.) What test would you perform to confirm the accuracy of your identification in (b.)? What would you observe as a result of the test, if your identification were correct?
to a soultion of the unknown, add some of the Cl2(aq)
then add somme dissolved starch
the production of a dark blue to black confirms iodine was made
(no organic layer used)