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Standard XII

Chemistry

Deliquescence and Alkaline Earth Metal Halides

Few drops of ...

Question

Few drops of $H N O_{3}$ are added to the II group before proceeding to the III group cation analysis to:

None of these

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precipitate III group cation

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convert

F e^{2 +}

F e^{3 +}

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convert

F e^{3 +}

F e^{2 +}

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Solution

The correct option is C convert $F e^{2 +}$ to $F e^{3 +}$
Group III cations- $A l^{3 +}, F e^{3 +}, C r^{3 +}$
Since the ferric ion is precipitated at group III. Concentrated nitric acid is added to oxidize the $H_{2} S$ in the solution from Group II, to convert $F e^{2 +} t o F e^{3 +}$ because it precipitate as $F e (O H)_{3}$ in the solution.

Fe is precipitated as $F e (O H)_{3}$ not as $F e (O H)_{2}$ because ferrous hydroxide is more soluble in water than ferric hydroxide.

Hence, option (a) is correct.

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Similar questions

Q. Few drops of

H N O_{3}

are added to II group before proceedingto III group in order to :

In qualitative analysis,

{I I I}^{r d}

group includes

F e^{3 +}, A l^{3 +}

and

C r^{3 +}

. The group reagent is ammonium hydroxide in the presence of ammonium chloride.

N H_{4} C I

is added to suppress the ionisation of

N H_{4} O H

so that only the

I I I^{r d}

group radicals are precipitated as their insoluble hydroxide and not the

I V^{t h}

and

V^{t h}

group radicals as the solubility products of their hydroxides are much higher. Before adding group reagent to the filtrate of IInd group, one drop of concentrated

H N O_{3}

(oxidising agent) is added and the content is boiled for 2-3 minutes and then cool because the solubility product of

F e (O H)_{2}

is very high as compared to

F e (O H)_{3}

. When a light bluish-green crystalline double salt-containing cations of III

^{r d}

group and zero groups are analysed. it responds to the following tests/reactions.
(a) Its aqueous solution gives a reddish-brown precipitate with an alkaline solution of potassium tetraiodomercurate (II)
(b) Its aqueous solution after boiling with conc.

H N O_{3}

gives a reddish-brown precipitate with sodium hydroxide.
(c) The solution of reddish-brown precipitate in oil.HCI gives blood red colouration with ammonium sulphocyanide and Prussian blue with potassium ferrocyanide.
(d) It's a very dilute solution gives a white precipitate with

(C H_{3} C O O)_{2} P b

solution and a white precipitate are only soluble in hot ammonium acetate.

Why one mL conc.

H N O_{3}

is added to

I I^{n d}

group filtrate before proceeding for

I I I^{r d}

group radicals?

Q. To precipitate group III cations

N H_{4} C l

should be added to the solution before the addition of ammonium hydroxide. Explain why.

Q. Addition of one drop of

{H N O}_{3}

in group (III) analysis is to oxidise

{F e}^{2 +}

{F e}^{3 +}

If the given statement is true enter 1 else enter 0.

Q. In the precipitation of the iron group in qualititative analysis, ammonium chloride is added before adding ammonium hydroxide to

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Few drops of HNO3 are added to the II group before proceeding to the III group cation analysis to:

Few drops of $H N O_{3}$ are added to the II group before proceeding to the III group cation analysis to: