FRANK Solutions for Class 10 Chemistry Chapter 12 - Practical Work

Chapter 12 - Practical Work Exercise 307

Question 1

Solution 1

Question 2

Solution 2

Question 3

Solution 3

Question 4

Solution 4

Question 5

Solution 5

Question 6

Write sqauential observation for effect of heat on

(a) Copper nitrate

(b) Lead carbonate

(c) Ammonium chloride

Solution 6

(a) i) Bluish green crystalline solid, on heating, melts to form a bluish green mass and gives off steamy vapours which condense on the cooler part of the test tube.

 ii) On further heating, the bluish green mass changes to a black residue.

 iii) It gives off a reddish brown gas and gives a gas which rekindles a glowing splinter, i.e. oxygen.

(b) i) A white solid turns yellow on heating.

 ii) Gives off a gas which extinguishes a burning wooden splinter.

 iii) Gas evolved turns lime water milky.

(c) i) When ammonium chloride is heated in a test tube, the lighter ammonia gas will emerge first and turn a piece of moist red litmus paper blue.

 ii) Hydrogen chloride coming up next will change the  

 litmus paper from blue back to red.

Question 7

Solution 7

Question 8

Solution 8

Chapter 12 - Practical Work Exercise 308

Question 1

Solution 1

Question 2

Solution 2

Question 3

Solution 3

Question 4

Solution 4

Question 5

Solution 5

Question 6

Solution 6

Question 7

Solution 7

Chapter 12 - Practical Work Exercise 309

Question 1

Solution 1

Question 2

Solution 2

Question 3

Solution 3

Question 4

Solution 4

Chapter 12 - Practical Work Exercise 310

Question 1

Solution 1

Question 2

Solution 2

Question 3

Solution 3

Chapter 12 - Practical Work Exercise 311

Question 1

Solution 1

Question 2

Select from the list given (a to e) one substances in each case which matches the description given in parts (i) to (v). (Note : Each substance is used only one in the answer)

(a) Nitroso Iron (II) Sulphate

(b) Iron (III) chloride

(c) Chromium sulphate

(d) Lead (II) chloride

(e) Sodium chloride

(i) A compound which is deliquescent

(ii) A compound which is insoluble in cold water, but soluble in hot water

(iii) The compound responsible for the brown ring during the brown ring test of nitrate iron

(iv) A compound whose aqueous solution is neutral in nature

(v) The compound which is responsible for the green colouration when sulphur dioxide is passed through acidified potassium dichromate solution

Solution 2

(i) Iron (III) chloride

(ii) Lead (II) chloride

(iii)Nitroso iron (II) sulphate

(iv)Sodium chloride

(v) Chromium sulphate

Question 3

What would you observe in the following cases:

Ammonium hydroxide is first added in a small quantity and then in excess to a solution of copper sulphate.

Solution 3

On addition of ammonium hydroxide in a small quantity, a blue-coloured copper hydroxide precipitate is formed. This copper hydroxide of light blue colour dissolves in excess of ammonium hydroxide to yield a deep blue solution.

Question 4

Sodium hydroxide solution is added to the solutions containing the ions mentioned in List X. List Y gives the details of the precipitate. Match the ions with their coloured precipitates.

List X	List Y
(i) Pb2+ (ii) Fe2+ (iii) Zn2+ (iv) Fe3+ (v) Cu2+ (vi) Ca2+	(A) Reddish Brown (B) White insoluble inexcess (C) Dirty green (D) White soluble in excess (E) White soluble in excess (F) Blue

Solution 4

(i) D

(ii) C

(iii) E

(iv) A

(v) F

(vi) B 

Chapter 12 - Practical Work Exercise 312

Question 1

State two observations when

(i) Lead nitrate crystals are heated in a hard glass test tube.

(ii) A few crystals of KNO₃ are heated in a hard glass tube

Solution 1

(i) Lead nitrate decrepitates on heating; a yellow solid is formed and it fuses with glass. Lead nitrate decomposes to lead oxide, nitrogen dioxide and oxygen. 

(ii) Oxygen is evolved.

  2KNO₃→ 2KNO₂ + O₂

Question 2

Give a chemical test to distinguish between the following pairs of compounds:

(i) Sodium chloride solution and sodium nitrate solution

(ii) Hydrogen chloride gas and hydrogen sulphide gas

(iii) Calcium nitrate gas and sulphur diaoxide gas

(iv) Carbon dioxide gas and sulphur dioxide gas

Solution 2

(i) Add silver nitrate solution to both solutions. Sodium chloride will form a curdy white ppt., whereas sodium nitrate will not undergo any reaction.

(ii) Hydrogen chloride gas gives thick white fumes of ammonium chloride when a glass rod dipped in ammonia solution is held near the vapour of the acid, whereas no white fumes are observed in case of hydrogen sulphide gas.

(iii) Calcium nitrate forms no ppt. even with addition of excess of NH₄OH, whereas zinc nitrate forms a white gelatinous ppt. which dissolves in excess of NH₄OH.

(iv) Carbon dioxide gas has no effect on acidified KMnO₄ or K₂Cr₂O₇, but sulphur dioxide turns potassium permanganate from pink to colourless.

Question 3

Distinguish between the following pairs of compounds using the test given with brackets :

Dilute sulphuric acid and dilute hydrochloric acid (using barium chloride solution)

Solution 3

 Sulphuric acid precipitates the insoluble sulphate of barium from the solution of barium chloride.

BaCl₂ + H₂SO₄→ BaSO₄ + 2HCl

Dilute HCl does not react with barium chloride solution, and thus, no precipitate is produced in the reaction.

Question 4

State the inference drawn from the following observations :

(i) On Carrying out the flame test with a salt P a brick red flame was obtained. What is the cation in P?

(ii) A gas Q turns moist lead acetate paper silvery black. Identify the gas Q.

(iii) pH of liquid R is 10. What kind of substance is R?

(iv) Salt S is prepared by reacting dilute sulphuric acid with copper oxide Identify S.

Solution 4

(i) On carrying out the flame test with a salt P, a brick red flame is obtained. Hence, the cation P is Ca²⁺.

(ii) A gas Q turns moist lead acetate paper silvery black. Hence, the gas is H₂S.

(iii) pH of liquid R is 10. Hence, substance R is a base.

(iv) Salt S is prepared by reacting dilute sulphuric acid with copper oxide. Hence, salt S is copper sulphate. 

Question 5

State your observation in each of the following cases:

(i) When dilute hydrochloric acid is added to sodium carbonate crystals

(ii) When excess sodium hydroxide is added to calcium nitrate solution

(iii) At the cathode when acidified aqueous copper sulphate solution is electrolyzed with copper electrodes

(iv) When calcium hydroxide is heated with ammonium chloride crystals

(v) When moist starch iodide paper is introduced into chlorine gas

Solution 5

(i) Sodium carbonate crystals on reaction with dilute HCl form sodium chloride, water and carbon dioxide, which is evolved with brisk effervescence. This is a neutralisation reaction as sodium carbonate is a basic salt, while hydrochloric acid is an acid. The chemical equation for this reaction is as follows:

 Na₂CO₃ + 2HCl → 2NaCl +H₂O + CO₂

(ii) Calcium nitrate solution on reaction with excess of sodium hydroxide produces calcium hydroxide and sodium nitrate. Calcium nitrate reacts with excess of sodium hydroxide to form a white precipitate of calcium hydroxide, which is sparingly soluble, and colourless sodium nitrate. The reaction is as follows:

 Ca(NO₃)₂ + 2NaOH → Ca(OH)₂ + 2NaNO₃

(iii) Acidified aqueous copper sulphate solution is electrolysed with copper electrodes by electrolysis. The electrolysis of an aqueous solution of copper sulphate using copper electrodes (i.e. using active electrodes) results in the transfer of copper metal from the anode to the cathode during electrolysis. Copper sulphate is ionised in aqueous solution.

 Chemical equation:

 CuSO₄ → Cu²⁺ + SO₄^2- 

 The positively charged copper ions migrate to the cathode, where each gains two electrons to become copper atoms which are deposited on the cathode.

 Cu²⁺ + 2e^- → Cu  

  Hence, the colour of copper sulphate changes from blue to colourless.

(iv) When ammonium chloride is heated with calcium hydroxide, ammonia gas is released.  

 2NH₄Cl + Ca(OH)₂→ CaCl₂ + 2NH₃ + 2H₂O

 The liberated gas turns red litmus blue.

(v) When moist starch iodide paper is introduced into chlorine gas, chlorine oxidises iodide to iodine, which shows up as blue when it forms a complex with starch. 

Question 6

The following table shows the tests a student performed on four different aqueous solutions which are X,Y,Z and W. Based on the observations provided, Identify the cation present

Chemical Test	Observation	Conclusion
To Solution X, ammonium hydroxide is added in minium quantity first and then in excess	A dirty white precipitate is formed which dissolves in excess to form a clear solution	(i)
To Solution Y, ammonium hydroxide is added in minimum quantity first and then in excess	A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution	(ii)
To solution W, A small quantity of sodium hydroxide solution is added and then in excess	A white precipitate is formed which remains insoluble	(iii)
To a salt Z, calcium hydroxide solution is added and then heated	A pungent smelling gas turning moist red litmus paper blue is obtained	(iv)

Solution 6

(i) Zn²⁺

(ii) Cu²⁺

(iii) Ca²⁺

(iv) NH₄⁺ 

Chapter 12 - Practical Work Exercise 313

Question 1

Identify the anion present in each of the following compounds :

(i) A salt M on treatment with concentrated sulphuric acid produces a gas which fumes in moist air and gives dense fumes with ammonia

(ii) A salt D on treatment with dilute sulphuric acid produces a gas which turns lime water milky but has no effect on acidified potassium dichromate solution

(iii) When barium chloride solution is added to salt solution E a white precipitate insoluble in dilute hydrochloric acid is obtained

Solution 1

(i) Chloride ion (Cl^-)

(ii) Carbonate (CO₃^2-)

(iii) Sulphate (SO₄^2-) 

Question 2

From the list of the following salts choose the salt that most appropriately fits the description given in the following :

[AgCl,MgCl₂,NaHSO₄,PbCO₃,ZnCO₃,KNO₃,Ca(NO₃)₂]

(i) A deliquescent salt

(ii) An insoluble chloride

(iii) On heating this salt gives a yellow residue when hot and white when cold

(iv) On heating this salt, a brown coloured to prepare the following salts:

Solution 2

(i) A deliquescent salt: MgCl₂

(ii) An insoluble chloride: AgCl

(iii) On heating, this salt gives a yellow residue when hot and a white residue when cold: ZnCO₃

(iv) On heating this salt, a brown-coloured gas is evolved: Ca(NO₃)₂ 

Question 3

Give balanced chemical equations to prepare the following salts:

(i) Lead sulphate from lead carbonate

(ii) Sodium sulphate using dilute sulphuric acid

(iii) Copper chloride using copper carbonate

Solution 3

(i) 

(ii) 

(iii) 

Question 4

Identify the cations in each of the following case:

(i) NaOH solution when added to solution (A) gives a reddish brown precipitate

(ii) NH₄OH solution when added to solution (B) gives white ppt. which does not dissolve in excess.

(iii) NaOH solution when added to solution (C) gives white ppt. which insoluble in excess

Solution 4

(i) Fe³⁺ ion

 

(ii) Pb²⁺ ion

(iii)  Ca²⁺ ion

   

Question 5

Identify the gas evolved and give the chemical test in each of the following cases:

(i) Dilute hydrochloric acid reacts with sodium sulphite

(ii) Dilute hydrochloric acid reacts with iron (II) sulphide

Solution 5

(i) Sulphur dioxide

 Freshly prepared K₂Cr₂O₇ paper changes from orange to green.

(ii) Hydrogen sulphide

 The gas released has a rotten egg smell.

Question 6

Identify the salts P and Q from the observations given below:

(i) On performing the flame test salt P produces a lilac coloured flame and its solution gives a white precipitate with silver nitrate solution. Which is soluble in ammonium hydroxide solution.

(ii) When dilute HCl is added to a salt Q, a brisk effervescence is produced and the gas turns lime water milky. When NH₄OH soltion is added to the above mixture (after adding dilute HCl), it produces a white precipitate which is soluble in excess NH₄OH solution.

Solution 6

(i) KCl

(ii) ZnCO₃