A) addition of \[N{{H}_{4}}OH\] in the presence of \[N{{H}_{4}}Cl\] when only \[Fe{{(OH)}_{3}}\] is precipitated
B) addition of \[N{{H}_{4}}OH\]) in the presence of \[N{{H}_{4}}Cl\]I when \[Cr{{(OH)}_{3}}\] and \[Fe{{(OH)}_{3}}\] both are precipitated and on adding \[B{{r}_{2}}\] water and NaOH, \[Cr{{(OH)}_{3}}\] dissolves
C) precipitate of \[Cr{{(OH)}_{3}}\] and \[Fe{{(OH)}_{3}}\] as obtained in (b) are treated with cone. HCI when only \[Fe{{(OH)}_{3}}\] dissolves
D) Both (b) and (c)
Correct Answer: B
Solution :
If \[F{{e}^{+}}\] and \[C{{r}^{3+}}\] both are present then very first solid ammonium chloride and ammonium hydroxide is added slowly till the solution smells of ammonia. \[F{{e}^{3+}}\] and \[C{{r}^{3+}}\] precipitates in the hydroxide form. For identification precipitate is treated with \[NaOH\] and \[B{{r}_{2}}\] water, yellow colouration confirms \[C{{r}^{3+}}\] ion. \[2NaOH+B{{r}_{2}}\xrightarrow{{}}NaBrO+NaBr+{{H}_{2}}O\] \[NaBrO\xrightarrow{{}}NaBr+[O]\] \[2Cr{{(OH)}_{2}}+4NaOH+3O\xrightarrow{{}}\] \[2Na{{C}_{2}}r{{O}_{4}}+5{{H}_{2}}O\] Solution is acidified and treated with lead acetate solution \[N{{a}_{2}}Cr{{O}_{4}}+Pb{{(C{{H}_{3}}COO)}_{2}}\xrightarrow{{}}\underset{\left( \text{Yellow ppt}. \right)}{\mathop{PbCr{{O}_{4}}}}\,\] \[+2C{{H}_{3}}COONa\]
You need to login to perform this action.
You will be redirected in
3 sec
