For each of the following pairs of Group III cations, you are given an unknown and...

For each of the following pairs of Group III cations, you are given an unknown and told that it contains one of te two cations. Describe a simpe test to determine which cation is present in each case. (Unless otherwise noted, assume they are aqueous solutions.

A. Al +3 and Fe +3

B. Fe (OH)3 (s) and Ni(OH)2 (s)

C. Cr +3 and Al +3

IN CLEAR HANDWRITING PLEASE!!

Solutions

Expert Solution

A. Al+3 & Fe+3

Aqueous solution of unknown salt is prepared. Then ammonium chloride and ammonium hydroxide is added into solution. Ammonium hydroxide is used as buffer base. Formation of reddish-brown precipitate will confirm about presence of Fe+3 cation. A gelatinous white precipitate shows Al+3 cation.

B. Fe(OH)3 & Ni(OH)2

In 1st salt, cation present is Fe+3, and in 2nd salt, cation present is Ni+2.

Adding extremely dilute hydrochloric acid, will cross check presence of both salts, if yellow precipitate or such coloured solution is formed, it will confirm presence of Fe+3. If its Ni+2 ion, it is showing green coloured solution in test tube or flask.

C. Cr+3 & Al+3

As said earlier in first case, after preparing aqueous solution of unknown salt, ammonium hydroxide and ammonium chloride is added into this solution. If gelatinous white precipitate is observed, Al+3 ion is present in solution while green precipitate shows about Cr+3 ion but it must be confirmed by adding sodium hydroxide as there may be presence of Fe+2 ion. After adding sodium hydroxide in excess of green precipitate, if it dissolves precipitate, it will confirm about Cr+3 otherwise it's a Fe+2 ion present in solution.

queen_honey_blossom answered 1 year ago

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