Selina Concise Chemistry Class 10 ICSE Solutions Chapter 4 - Analytical Chemistry: Uses of Ammonium Hydroxide And Sodium Hydroxide

Selina Concise Chemistry Class 10 ICSE Solutions Analytical Chemistry: Uses of Ammonium Hydroxide And Sodium Hydroxide 

Selina Concise Chemistry Class 10 ICSE Solutions Analytical Chemistry: Uses of Ammonium Hydroxide And Sodium Hydroxide

Exercise 4

1.Write the probable colour of the following salts?

(a) Ferrous salts

(b) Ammonium salts

(c) Cupric salts

(d) Calcium salts

(e) Aluminium salts

Solution 1.

(a) Ferrous salts : Light green
(b) Ammonium salts : Colourless
(c) Cupric salts : Blue
(d) Calcium salts : Colourless
(e) Aluminium salts : Colourless


2.Name:

(a) a metallic hydroxide soluble in excess of NH4OH.

(b) a metallic oxide soluble in excess of caustic soda solution.

(c) a strong alkali.

(d) a weak alkali.

(e) Two colourless metal ions.

(f) Two coloured metal ions.

(g) a metal that evolves a gas which burns with a pop sound when boiled with alkali solutions.

(h) Two bases which are not alkalis but dissolve in strong alkalis.

(i) a coloured metallic oxide which dissolves in alkalis to yield colourless solutions.

(j) a colourless cation not a representative element.

Solution 2.
(a) Cu(OH)2
(b) ZnO
(c) NaOH
(d) NH4OH
(e) Na+, Ca2+
(f) Fe2+, Mn2+
(g) Aluminium
(h) Zn(OH)2 and Al(OH)3
(i) PbO
(j) Ammonium ion

3.Write balanced equations for Aluminium and  PbO.

Solution 3.

4.What happens when ammonia solution is added first dropwise and then inexcess to the following solutions:

(i) CuSO₄(ii)ZnSO₄(iii)FeCl₃

Write balanced equations for these reactions.

Solution 4.

5.What do you observe when caustic soda solution is added to the following solution: first a little and then in excess.

(a) FeCl₃ ,

(b) ZnSO₄,

(c) Pb(NO₃)₂ ,

(d) CuSO₄?

Write balanced equations for these reactions.

Solution 5.

6.Name the chloride of a metal which is soluble in excess of ammonium hydroxide. Write equation for the same.

Solution 6.

7.On adding dilute ammonia solution to a colourless solution of a salt, a white gelatinous precipitate appears. This precipitate however dissolves on addition of excess of ammonia solution. Identify (choose from Na, Al, Zn, Pb, Fe)

(a) Which metal salt solution was used?

(b) What is the formula of the white gelatinous precipitate obtained?

Solution 7.

(a) ZnCl2
(b) Zn(OH)2

8.Name:

(a) A yellow monoxide that dissolves in hot and concentrated caustic alkali.

(b) A white, insoluble oxide that dissolves when fused with caustic soda or caustic potash.

(c) A compound containing zinc in the anion.

Solution 8.

(a) PbO
(b) ZnO
(c) K2ZnO2

9.Select the correct answers:

(a) Colour of an aqueous solution of copper sulphate is

(i) Green

(ii) Brown

(iii) Blue

(iv) Yellow

(b) Colour of the precipitate formed on adding NaOH solution to iron (II) sulphate solution is

(i) White

(ii) Brown

(iii) Green

(iv) Pale blue

(c) A metal which produces hydrogen on reacting with alkali as well as with acid.

(i) Iron

(ii) Magnesium

(iii) Zinc

(iv) Copper

Solution 9.

10.What do you observe when freshly precipitated aluminum hydroxide reacts with caustic soda solution?Give balanced equation.

Solution 10.

When freshly precipitated aluminum hydroxide reacts with caustic soda solution, whitesalt of sodium meta aluminate is obtained.

11.

Solution 11.

12.

Solution 12.

With excess of NaOH, white gelatinous ppt. of Zn (OH)2 is soluble. So, these two cannot be distinguished by NaOH alone. However white ppt. of Pb(OH)2 is readily soluble in acetic acid also.

(i) On addition of NH4OH to calcium salts no precipitation of Ca(OH)2 occurs even with addition of excess of NH4OH because the concentration of OH–ions from ionization of NH4OH is so low that it cannot precipitate the hydroxide of calcium.

Pb(NO3)2+2 NH4OHPb(OH)2+2NH4NO3

13.

Solution 13.

Lead carbonate is dissolved in dilute nitric acid and then ammonium hydroxide is added to it. A white precipitate is formed which is insoluble in excess.

Zinc carbonate is dissolved in dilute nitric acid and then ammonium hydroxide is added to it. A white precipitate is formed which is soluble in excess.

14.

Solution 14.

Reagent bottles A and B can identified by using calcium salts such as Ca(NO3)2.

On adding NaOH to Ca (NO3)2, Ca (OH)2 is precipitated as white precipitate which is sparingly soluble in excess of NaOH.

Ca(NO3)2+2NaOH → Ca(OH)2+ 2NaNO3

Whereas, on addition of NH4OH to calcium salts, no precipitation of Ca(OH)2 occurs even with addition of excess of NH4OH because the concentration of OH–ions from the ionization of NH4OH is so low that it cannot precipitate the hydroxide of calcium.

So the reagent bottle which gives white precipitate is NaOH and the other is NH4OH.

Intext Exercise

1.What do you understand by the following:

(i) Analysis,

(ii) Qualitative analysis,

(iii) Reagent,

(iv) Precipitation?

Solution 1.

(i) Analysis: The determination of chemical components in a given sample is called analysis.

(ii) Qualitative analysis: The analysis which involves the identification of the unknown substances in a given sample is called qualitative analysis.

(iii) Reagent: A reagent is a substance that reacts with another substance.

(iv) Precipitation: It is the process of formation of an insoluble solid when solutions are mixed. The solid thus formed is called precipitate.

2.Write the probable colour of the following salts:

(i) Iron (III) chloride,

(ii) Potassium nitrate,

(iii) Ferrous sulphate,

(iv) Aluminum acetate,

Solution 2.

(i) Yellow
(ii) Colourless
(iii) PaleGreen
(iv) Colourless


3.

Solution 3.

(i) Fe3+
(ii) Cu2+
(iii) Cu+2
(iv) Mn2+

4.

Solution 4.

(i) Ca(OH)2
(ii) Fe(OH)2 and Cu(OH)2
(iii) Zn(OH)2 and Pb(OH)2

5.What do you observe when an ammonium salt is heated with caustic soda solution? Write the word equation.

Solution 5.

6.How will you distinguish NH₄OH solution from NaOH solution?

Solution 6.

NH4OH and NaOH can be distinguished by using calcium salts.

For example on adding NaOH to Ca(NO3)2, Ca(OH)2 is obtained as white precipitate which is sparingly soluble in excess of NaOH.

Ca(NO3)2 + 2NaOH → Ca(OH)2 + 2NaNO3

On addition of NH4OH to calcium salts, no precipitation of Ca(OH)2 occurs even with the addition of excess of NH4OH.This is because the concentration of OH– ions from the ionization of NH4OH is so low that it cannot precipitate the hydroxide of calcium.

7.

Solution 7.

(i) Fe(OH)2 and Pb(OH)2
(ii) Cu(OH)2 and Zn(OH)2

Selina Concise Chemistry Class 10 ICSE Solutions Chapter 4 - Analytical Chemistry: Uses of Ammonium Hydroxide And Sodium Hydroxide