Frank Chapter 3 Study of Acids, Bases and Salts ICSE Solutions and MCQ Class 10 Chemistry

Frank Solutions for Chapter 3 Study of Acids, Bases and Salts Class 10 Chemistry ICSE

1. Define an acid.

Answer 

An acid is defined as a compound which when dissolved in water produces hydronium ion (H₃O⁺), the only positively charged ion and a negative ion. At first the acid furnishes hydrogen ion (H⁺) in aqueous solution but this H⁺ ion combines with a water, molecule to form Hydronium ion.
For example : acetic acid, sulphuric acid, nitric acid.
CH₃COOH + H₂O → H₃O⁺ + CH₃COO^-

2. Give the name and formula of two
(a) Strong monobasic acids
(b) Weak dibasic acids
(c) Non-volatile acids
(d) Volatile acids

Answer 

(a) (i) Hydrogen chloride HCl
(ii) Nitric acid HNO₃

(b) (i) Carbonic acid H₂CO₃
(ii) Oxalic acid (COOH)₂

(c) (i) Sulphuric acid H₂SO₄
(ii) Hydrogen chloride HCl

(d) (i) Carbonic acid H₂CO₃
(ii) Acetic acid

3. (a) Define a base.
(b) Explain, all alkalis are bases but all bases are not alkalis.

Answer 

(a) A base is defined as a chemical compound which when reacts with hydronium ion or H⁺  ions furnished by an acid to form salt and water only.
For example: CuO, Mg (OH)₂

(b) An alkali is a base which is soluble in water but all bases are not water soluble.
For example Ferric hydroxide [Fe (OH)₃] and cupric hydroxide (Cu (OH)₂] are bases but these are not soluble in water but sodium hydroxide NaOH, calcium hydroxide Ca(OH)₂ are bases and are also soluble in water.
Hence it is rightly said that all alkalis are bases but all bases are not alkalis.
Concept Insight: An alkali is a basic hydroxide which when dissolved in water produces hydroxyl (OH') ions as the only negatively charged ions.
Example: Na0H(aq) ⇌ Na⁺  + OH⁺  

4. (a) Define pH.
(b) State three applications of pH scale.

Answer 

(a) The pH of a solution is defined as the negative logarithm (base 10) of the hydronium ion concentration present in the solution.
pH = -log₁₀ [H₃O⁺ ]
(b) The three applications of pH scale are:
It is used to determine the acidic or basic nature of the solution.
It is used to determine hydronium ion concentration present in the solution.
It is used to find out neutrality of the solution.

5. (a) Define an indicator.
(b) Explain, why a universal indicator is preferred to acid-base indicators.

Answer 

(a) Indicators are organic compounds which when added in small amounts to a solution; indicate the nature (acidity or alkalinity) of the solution. 
(b) Universal indicators are preferred to acid - base indicators because these give different colours in different pH ranges. A solution containing a drop of universal indicator is matched against a standard colour chart to find the pH of the solution.

pH range	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Colour of universal indicator		Red		Pink		Yellow		Green		Blue		Indigo		Violet

6. What is the difference between:
(a) An alkali and a base?
(b) An alkali and a metal hydroxide?

Answer 

The difference between an alkali and a base is  : 

An alkali	Base
An alkali is a basic hydroxide which when dissolved in water produces hydroxyl (OH- ) ions as the only negatively charged ions.	A base is defined as a chemical compound which when reacts with hydronium ion or H+  ions furnished by an acid form salt and water only.
All alkalis are water soluble.	Bases may or may not be water soluble.
Examples are NaOH, KOH, Ca (OH)2.	Examples are CuO, Mg (OH),.

(b)

An alkali	Metal hydroxide
An alkali is a basic hydroxide which when dissolved in water produces hydroxyl (OH-) ions as the only negatively charged ions.	Metal hydroxides are generally bases which have a metal atom bonded to a hydroxide ion (OH- ).
Examples NaOH, KOH.	Examples Mg (OH)2

7. Name the ions furnished by
(a) Bases in solution
(b) a weak alkali
(c) an acid

Answer

(a) Base in solution furnishes the ions:
Hydroxide ion/oxide ion and a metallic ion.
(b) A weak alkali furnishes the ions:
Hydroxide ion and metallic ion and molecules of weak alkali./
(c) An acid in a solution furnishes the ions:
Hydronium/Hydrogen ion and a negative ion.

8. Explain hydronium ion. Write the ionization of sulphuric acid showing the formation of hydronium ion.

Answer 

Hydronium ion : Hydronium ion is H₃O⁺ . 
It is formed when a hydrogen ion H⁺ released from an acid combines with a water molecule as : 
H⁺ + H₂O ⟶ H₃O⁺ 
In hydronium ion, hydrogen ion is linked to water molecule via coordinate bond which is formed by the participation of lone pair of electrons present on oxygen atom. The structure of hydronium ion is as : 

9. Give one example in each case:
(a) Basic oxide which is soluble in water
(b) A hydroxide which is highly soluble in water.
(c) A basic oxide which is insoluble in water.
(d) A hydroxide which is insoluble in water.
(e) A weak mineral acid.
(f) A base which is not an alkali.
(g) An oxide which is a base.
(h) A hydrogen containing compound which is not an acid.

Answer 

(a) CaO
(b) NaOH
(c) CuO
(d) Cu[(OH)₂]
(e) H₂CO₃
(f) Ferric hydroxide [Fe (OH)₃].
(g) CuO
(h) NH₃

10. Anhydrous hydrogen chloride is not an acid but its aqueous solution is a strong acid. Explain.

Answer

Anhydrous hydrogen chloride is not an acid but its aqueous solution is a strong acid because anhydrous means without water and we know that the property of acidity is shown by a substance only when it is dissolved in water or its aqueous solution is prepared.

11. Carbonic acid gives an acid salt but hydrochloric acid does not. Explain.

Answer 

Carbonic acid is a dibasic acid i.e. H₂CO₃ . So when it reacts with a base such as NaOH then there is only partial replacement of hydrogen ions of carbonic acid by sodium ion to form an acid salt as:
H₂CO₃ + NaOH → NaHCO₃ + H₂O
In case of hydrogen chloride which is a monobasic acid the salt produced will be normal as:
HCI + NaOH → NaCI + H₂O
Concept Insight: Salts formed by partial replacement of hydrogen ions of acid by metallic ions are called acid salts. 

12. What do you understand by the strength of an acid? On what factors does the strength of an acid depend?

Answer 

Strength of an acid measures the ease with which the acid can ionize to produce hydrogen or hydronium ions when dissolved in water. Those acids which can easily ionize to form hydrogen ions are called strong acids while those which can partially ionize to form hydrogen ions are called weak acids.
Strength of an acid depends upon many factors such as:
Molecular structure of the acid
The temperature
Properties of the solvent

13. How is an acid prepared from a non metal and a base from a metal? Give equation.

Answer 

(i) Acid from a non metal:
Certain non metals like sulphur (S), phosphorous (P), can be oxidized by concentrated nitric acid to yield corresponding acid.
Non metal + Acid — Acid + Water + Oxide

S + 6HNO₃ → H₂SO₄ + 2H₂O + 6NO₂ 

(ii) Base from a metal:
Active metals like K, Na, Ca react with water to produce water soluble bases. These bases are called alkalis.
Active metal + water — Base / Alkali + Hydrogen
2Na + 2H₂O — 2NaOH + H₂ 

14. Two solutions A and B have pH values of 2 and 9 respectively which one of these two will give a pink colour with phenolphthalein indicator?

Answer 

Solution B with pH value 9 will give pink colour with phenolphthalein.
Concept Insight: Bases give pink colour with phenolphthalein because a base will abstract two protons from phenolphthalein and the resulting phenolphthalein ion provides pink colour to the solution.

15. Name two indicators which can identify the presence of an acid?

Answer 

Two indicators for identification of acid are methyl red and Thymol blue.

16. State how would you prepare copper (II) oxide from
(a) Copper nitrate
(b) copper carbonate
(c) copper sulphate

Answer 

17. Give four examples of preparation of acids by synthesis.

Answer 

Preparation of acids by synthesis follows general reaction :
Hydrogen + Non metal ⟶ Acid 

(i) H₂ + I₂ → 2HI
(ii) H₂ + Br₂ → 2HBr
(iii) H₂ + Cl₂ → 2HCl
(iv) H₂ + S → H₂S

18. (a) Define an acid salt and a normal salt.
(b) How many salts can be obtained from ortho phosphoric acid? Is there any difference in the salts formed by the acid?

Answer 

(a) Acid salt. The salt formed by the partial replacement of the replacable hydrogen atoms of an acid molecule by a metallic or ammonium ion is called acid salts. For example NaHSO₄ , Na₂HPO₄ 
Normal salt: The salt formed by replacement of all the replaceable hydrogen atoms of an acid by metallic or ammonium ions is called a normal salt. For example NaCI, Na₂SO₄ 
(b)Ortho phosphoric acid is H₃PO₄  i.e. a tribasic acid has three replaceable hydrogen atoms so it forms three series of salts, namely two acid salts and a normal salt, with NaOH as: 

NaOH + H₃P0₄ ⟶ NaH₂P0₄  + H₂0
Acid salt (Monosodium hydrogen salt)

2NaOH + H₃P0₄ ⟶ Na₂HPO₄  + 2H₂0 
Acid salt (Disodium hydrogen phosphate) 

3NaOH + H₃P0₄ ⟶  Na₃PO₄   + 3H₂0  
Normal salt (Sodium phosphate) 

19. Give equations to prepare the following as directed:
(a) MgCO₃ from MgCl₂
(b) PbCO₃ from Pb(NO₃)
(c) NaHCO₃ from Na₂CO₃

Answer 

(a) MgCl₂ + Ca(OH)₂ + CaCl₂
Mg(OH)₂ + 2CO₂ → Mg(HCO₃)₂
Mg(HCO₃)₂ → MgCO₃ + CO₂ + H₂O
(b) Pb(NO₃)₂ + Na₂CO₃ → PbCO₃ + 2NaNO₃
(c) Na₂CO₃ + CO₂ + H₂O → 2NaHCO₃ 

20. Define the following terms:
(i) Efflorescence.
(ii) Hygroscopy.
(iii) Water of crystallization.

Answer 

(i) Efflorescence: It is the phenomenon by which hydrated salts on exposure to dry air, lose their water of crystallization and crumble to powder.
(ii) Hygroscopy: It is the phenomenon by which substances absorb moisture from air, but only sufficiently so as to become wet.
(iii) Water of crystallization: It is the fixed amount of water that is present in a crystal as an integral part of its constitution. Hydrated salts are salts having water of crystallisation.

21. What is deliquescence? What name is given to the compounds exhibiting such property?

Answer 

Deliquescence is the phenomenon by which certain salts absorb moisture from air, lose their water of crystallization and dissolve in it to form a saturated solution.
The substances which exhibit deliquescence are called deliquescent.
For example Caustic soda NaOH, Caustic potash KOH.

22. Explain salt hydrolysis. Name two salts which are (a) acidic (b) basic (c) neutral, when dissolved in water.

Answer 

Salt hydrolysis: The reaction between a salt and water to produce an acid or a base is called salt hydrolysis or hydrolysis. By hydrolysis the salt, we can find out its parent acid and parent base. 

For example: NaCI + H₂O →  Na⁺  + Cl⁺  
Salts which are acidic:

1. Ammonium sulphate
2. Ammonium chloride.

Salts which are basic:

1. Potassium carbonate
2. Sodium acetate.

Salts which are neutral:

1. Ammonium acetate
2. Ammonium carbonate. 

23. Give the preparation of the salt given in the left column by matching with the methods given in the right column. Write balanced equations for each preparation. 

Salt	Method of Preparation
Zinc sulphate Ferrous sulphide Barium sulphate Sodium sulphate	Precipitation Displacement Neutralization Synthesis

Answer 

Salt	Method of Preparation
Zinc sulphate Ferrous sulphide Barium sulphate Sodium sulphate	Displacement  Synthesis Precipitation Neutralization

24. (a) Why common salt gets wet during rainy season?
(b) Give four substances which contain water of crystallization and write their common name.

Answer

(a) Common salt gets wet during rainy season because the commercially available salt contains impurities, like magnesium chloride, which are deliquescent substances. These absorb moisture from atmosphere and make the table salt wet.

(b) (i) Na₂CO₃.10H₂O = Washing soda
(ii) MgSO₄.7H₂O = Epsom salt
(iii) CuSO₄.5H₂O = Blue vitriol
(iv) ZnSO₄.7H₂O = White vitriol

25. Write the reactions of SO₂ and oxides of nitrogen which leads to acid rain formation.

Answer 

26. Fill in the blanks
(a) The word acid comes from latin word acidus meaning _____
(b) Vinegar is the source of ______ acid.
(c) Magnesia is used in making ______.
(d) pH scale was introduced by ______ in 1909.
(e) ______ is the phenomenon by which hydrated salts on exposure to dry air, lose their water of crystallization and crumble to powder.

Answer 

(a) The word acid comes from the latin word acidus meaning 'sour'.
(b) Vinegar is the source of acetic acid.
(c) Magnesia is used in making refractory bricks.
(d) pH scale was introduced by Sorencen in 1909.
(e) Efflorescence is the phenomenon by which hydrated salts on exposure to dry air lose their water of crystallisation and crumble to powder.

27. Choose the correct answer from the options given below:
(i) Which of them occurs in solid state?
(a) Citric acid
(b) Formic acid
(c) Acetic acid
(d) Hydrochloric acid
Answer 
(a) Citric acid

(ii) Benzoic acid is used for/in/as
(a) Baking powder
(b) Food preservative
(c) Fertilizers
(d) Explosives
Answer 
(b) Food preservative

(iii) Which colour with the universal indicator indicates highly alkaline solution?
(a) Dark red
(b) Yellow
(c) Green
(d) Violet
Answer 
(c) Violet

(iv) Which one is the acidic salt?
(a) KNO₃
(b) Sodium acetate
(c) Calcium chloride
(d) Ammonium acetate
Answer 
(d) Calcium chloride

28. A solution has a pH of 7. Explain, how you would:
(i) Increase its pH
(ii) Decrease its pH
If a solution changes the color of litmus from red to blue, what can you say about its pH?

Answer 

1. pH of a solution having pH 7 can be increased by adding a base to it such as NaOH.
2. pH can be decreased by adding an acid such as HCl to it.

If a solution changes colour of litmus from red to blue, it shows that its pH is above 7.

29. What can you say about the pH of a solution that liberates carbon dioxide from sodium carbonate?

Answer 

The solution that liberates carbon dioxide from sodium carbonate has pH below 7 and hence acidic in nature. Since acids react with carbonates to liberate carbon dioxide gas as:
Carbonate + dil. Acid ⟶ Salt + Water + Carbon dioxide
For example: NaHCO₃ + HCI ⟶ NaCl + H₂O  + CO₂ 

30. From the list of the substances given, name the substances which you would use to prepare each of the following salts:
List of substances: Copper, lead, sodium, zinc, copper oxide, lead carbonate, sodium carbonate solution, dilute hydrochloric acid, dilute nitric acid and dilute sulphuric acid.
Salts: (a) zinc sulphate (b) copper sulphate (c) sodium sulphate (d) lead sulphate.

Answer 

(a) Zinc sulphate = Zinc and dilute sulphuric acid
(b) Copper sulphate = Copper oxide and dilute sulphuric acid
(c) Sodium sulphate = Sodium carbonate solution and dilute sulphuric acid
(d) Lead sulphate = Lead carbonate and dilute sulphuric acid

31. Define the meaning of the term 'acid salt'.

Answer 

The term acid salt means the salt formed by partial replacement of the hydrogens present in the acid by metallic or ammonium ions.
For example: NaHCO₃

32. (i) What is the purpose of the pH scale?
(ii) What is the pH of pure water?
(iii) A is a soluble acidic oxide; B is a soluble base. Compared to the pH of pure water, what is the pH of (a) a solution of A (b) a solution of B.

Answer 

(i) pH scale is used to express the acidic or basic nature of solution.
(ii) pH of pure water is 7 since it does not have any impurities.
(iii) (a) A soluble oxide of A will have pH less than the pH of pure water i.e. below 7.
(b) A solution of 'B' will have more pH than pure water i.e. above 7.

33. Taking sodium carbonate as an example, give the meaning of the following terms:
(i) Water of crystallization.
(ii) Anhydrous.

Answer 

(i) Water of crystallization: It is the fixed amount of water that is present in a crystal as an integral pat of its constitution. Compounds having water of crystallization are called hydrous salts.
For example: Sodium carbonate Na₂CO₃ has 10 molecules of water present as water of crystallization Na₂CO₃.10H₂O
(ii) Anhydrous: Hydrous salt on heating lose their water of crystallization, such salts are then called anhydrous.
For example: Na₂CO₃.10H₂O on losing 10 molecules of water forms Na₂CO₃.

34. Outline the steps required to convert hydrogen chloride to anhydrous iron (III) chloride. Write the equations for the reactions.

Answer 

MnO₂ + 4HCl (conc) → MnCl₂ + Cl₂ + 2H₂O.
Chlorine thus obtained is dried by passing through concentrated Sulphuric acid. This dried chlorine is passed over heated Iron to get anhydrous Iron (III) chloride.
2Fe (heated) + 3Cl₂ (dry) → 2FeCl₃

35. Answer the following questions below, relating your answers only to salts in the following list:
Sodium chloride, anhydrous calcium chloride, copper sulphate-5-water.
(i) What is the name given to the water in the compound copper sulphate-5-water?
(ii) If copper sulphate-5-water is heated, the water is driven off leaving anhydrous copper sulphate. What is the colour of anhydrous copper sulphate?
(iii) By what means, other than heating, you can dehydrate copper sulphate-5-water and obtain anhydrous copper sulphate?
(iv) Which one of the salts in the given list is deliquescent?

Answer 

(i) Water of cystallization.
(ii) White.
(iii) Efflorescence.
(iv) Sodium chloride.

36. What is meant by the term weak acid?

Answer 

Those acids which ionize partially in aqueous solution and thus they contain ions as well as molecules of the acid. Organic acid such as CH₃COOH, is a weak acid.

37. Solution P has a pH of 13, solution Q has a pH of 6, and a solution R has a pH of 2. Which solution:
(a) Will liberate ammonia from ammonium sulphate on heating?
(b) Is a strong acid.
(c) Contains molecules as well as ions?

Answer 

(a) Solution P with pH 13 will liberate ammonia from ammonium sulphate on heating: 
Ammonium salt  + alkali ⟶ Salt + Water + Ammonia. 
(b) Solution R with pH 2 is a strong acid. 
(c) Solution Q with pH 6 contains molecules as well as ions. 

38. Give the name and formula of the acid salt which gives sodium ions and sulphate ions in solution.

Answer 

The name and formula of the acid salt which gives sodium ions and sulphate ions in solution is Sodium hydrogen sulphate NaHSO₄.

39. (a) Define the following terms:
(i) Acid.
(ii) pH scale.
(iii) Neutralisation.
(b) (i) Outline the steps that would be necessary to convert insoluble lead (II) oxide into insoluble chloride.
(ii) Write the balanced equations for the reaction required to convert insoluble lead (II) oxide into insoluble lead chloride.
(iii) If iron reacts with dilute sulphuric acid, what will be the products?
(iv) A solution of iron (III) chloride has a pH less than 7. Is the solution acidic or alkaline?

Answer 

(a) (i) Acid: An acid is a compound which when dissolved in water produces hydronium ion (H3O⁺ ), the only positively charged ion and a negative ion.
(ii) pH scale: The scale over which a range of pH values from acidic to basic are arranged is called a pH scale.
(iii) Neutralisation : It is the process by which H⁺ ions of an acid react completely with water the [OH.] ions of a base to give salt and water only. 

For example 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

(b) (i) Treatment of lead dioxide with4 molecules of hydrochloric acid gives lead(II) chloride as well as chlorine gas

(ii) Steps required for this reaction are:

(iii) Iron reacts with dilute sulphuric acid as: 

Fe + H₂SO₄ → FeSO₄  + H₂ 

(iv) Since the value of pH is less than 7 so the solution will be acidic. 

40. Some methods used for the laboratory preparation of salts are : 
(a) Metal + acid 
(b) Carbonate + acid
(c) Precipitation 
(d) Direct combination 
(e) Titration 
Copy and complete the following table : 

Salt	Method of preparation
Ammonium sulphate Calcium carbonate Iron (III) chloride Lead nitrate Zinc sulphate

Answer 

Salt	Method of preparation
Ammonium sulphate Calcium carbonate Iron (III) chloride Lead nitrate Zinc sulphate	Titration Precipitation Direct combination Carbonate + acid Metal + acid

41. (a) Choosing only substances from the list given in the box below, write equations for the reactions which you would use in the laboratory to obtain:

Dilute sulphuric acid

Copper Iron Sodium, Zinc

Copper carbonate Sodium carbonate

(i) Sodium sulphate
(ii) Copper sulphate
(iii) Iron (II) sulphate
(iv) Zinc carbonate

(b) From the formulae listed below, choose one in each case corresponding to the salt having the given description:
AgCl, CuCO₃, CuSO₄, 5H₂O, KNO₃, NaCl, NaHSO₄, Pb(NO₃), ZnCO₃, ZnSO₄, 7H₂O 
(i) An acid salt
(ii) An insoluble chloride
(iii) On treating with concentrated sulphuric acid, this salt changes from blue to white. (d) On heating this salt changes from green to black
(iv) This salt gives nitrogen dioxide on heating 

(a) (i) Preparation of sodium sulphate
Sodium carbonate + dilute sulphuric acid ⟶ Sodium sulphate + water + carbon dioxide.
Na₂CO₃ + H₂SO₄ ⟶ Na₂SO₄ + H₂O + CO₂ 
(ii) Preparation of Copper sulphate:
Copper carbonate + dilute sulphuric acid ⟶ Copper sulphate + water + carbon dioxide .
CuCO₃ + H₂SO₄ ⟶ CuSO₄ + H₂O + CO₂ 
(iii) Preparation of iron (II) sulphate. 
Iron + dilute sulphuric acid ⟶ Iron (II) sulphate + Hydrogen 
Fe + H₂SO₄ ⟶ FeSO₄ + H₂     
(iv) Preparation of Zinc carbonate. 
Zn + H₂SO₄ (dil) ⟶ ZnSO₄ + H₂     
ZnSO₄ + Na₂CO₃ ⟶ ZnCO₃ +  Na₂SO₄ 

(b) (i) NaHSO₄ .
(ii) AgCl.
(iii) CuSO₄ . 5H₂O
(iv) CuCO₃ 
(v) Pb(NO₃)₂   

42. (a) Write the balanced equations for the preparation of the following compounds, starting from iron and using only one other substance:
(i) Iron (II) chloride
(ii) Iron (III) chloride
(iii) Iron (II) sulphate
(iv) Iron (II) sulphide
(b) Write the equations for the laboratory preparation of
(i) sodium sulphate using dilute sulphuric acid.
(ii) lead sulphate using dilute sulphuric acid.

Answer 

(a) (i) Fe + dilute HCl + FeCl₂ + H₂
(ii) 2Fe + 3Cl₂ → 2FeCl₃
(iii) Fe + dilute H₂SO₄ → FeSO₄ + H₂
(iv) Fe + S → FeS
(b) (i) 2NaOH + dilute H₂SO₄ → Na₂SO₄ + 2H₂O
(ii) Pb(OH)₂ + dilute H₂SO₄ → PbSO₄ + 2H₂O

43. Choosing the correct words given in brackets, complete the sentences given below:
(i) An acid is a compound which, when dissolved in water gives ______ ( hydronium / hydroxide) ions as the only ______ (positive/negative) ions.
(ii) A(n) ______ (acid/basic) salt is one in which the hydrogen of an acid has been partially replaced by a ______ (metal/non-metal).

Answer 

(i) Hydronium, positive
(ii) Acid, metal

44. Write equations for the laboratory preparation of the following salts, using sulphuric acid:
(i) Iron (II) sulphate from the iron.
(ii) Copper sulphate from copper.
(iii) Lead sulphate from lead nitrate.
(iv) Sodium sulphate from sodium carbonate.

Answer 

(i)Fe + dilute H₂SO₄ → FeSO₄ + H₂
(ii) Cu + conc. H₂SO₄ → CuSO₄ + 2H₂O + SO₂ 
(iii) Pb(NO₃)₂  + dilute H₂SO₄ →  PbSO₄ + 2HNO₃ 
Na₂CO₃ + dilute H₂SO₄ ⟶ Na₂SO₄ + 2H₂O + CO₂ 

45. Which of the following methods, (a), (b), (c), (d) or (e) is generally used for preparing the chlorides listed below from (i) to (v). Answer by writing down the chloride and the letter pertaining to the corresponding method. Each letter is to be used only once.
(a) Action of an acid on a metal.
(b) Action of an acid on an oxide or carbonate.
(c) Direct combination.
(d) Neutralization of an alkali by an acid.
(e) Precipitation (double decomposition).
(i) copper(II) chloride.
(ii) iron(III) chloride.
(iii) iron(II) chloride.
(iv) lead (II) chloride.
(v) sodium chloride.

Answer 

Methods for preparation:
(i) Preparation of copper(II) chloride.
Action of an acid on an oxide or carbonate
(ii) Preparation of iron(III) chloride.
 Direct combination
(iii) Preparation of iron (II) chloride.
Action of an acid on a metal
(iv) Preparation of lead (ii) chloride
Precipitation (double decomposition)
(v) Preparation of sodium chloride
Neutralization of an alkali by an acid.

46. The preparation of lead sulphate from lead carbonate is a two step process (lead sulphate cannot be prepared by adding dilute sulphuric acid to lead carbonate)
(a) What is the first step that is required to prepare lead sulphate from lead carbonate?
(b) Write the equation for the reaction that will take place when this first step is carried out.
(c) Why is the direct addition of dilute sulphuric acid to lead carbonate an impractical method of preparing lead sulphate?

Answer 

(a) Lead carbonate is first treated with dilute HNO₃ .
(b) PbCO₃ + 2HNO₃ → Pb(NO₃)₂ + H₂O + CO₂ 
(c) Lead carbonate and lead sulphate both are insoluble in water. So when dilute H₂SO₄ is added to lead carbonate, lead sulphate formed deposits on the remaining lead carbonate thereby stopping the further reaction.

47. Fill in the blanks with suitable words:
An acid is a compound which when dissolved in water forms hydronium ions as the only ______ ions.
A base is a compound which if soluble in water contains ______ ions. A base reacts with an acid to form ______ and water only. This type of reaction is known as ______.

Answer 

Positive,  hydroxyl,  Salt,  Neutralization.

48. What is observed when neutral litmus solution is added to sodium hydrogen carbonate solution?

Answer 

When neutral litmus solution is added to sodium hydrogen carbonate solution, litmus solution turns red

49. Mention the colour changes observed when the following indicators are added to acids:
(a) Alkaline phenolphthalein solution.
(b) Methyl orange solution.
(c) Neutral litmus solution.

Answer 

(a) From pink to colourless.
(b) From orange to pink.
(c) From colourless to red.

50. From the list given below. Select the word(s) required to correctly complete the blanks (i) to (v) in the following passage:
Ammonia, Ammonium, Carbonate, Carbon dioxide, Hydrogen, Hydronium,
A solution 'X' turns blue litmus red so it must contain (i) ______ ions; another solution 'Y' turns red litmus blue and therefore must contain(ii) ______ ions. When solutions X and Y are mixed together, the products will be a (iii) ______ and ______ (iv) ______. If a piece of magnesium was put into solution X, (v) ______ gas would be evolved.

Answer 

(i) Hydronium
(ii) Hydroxide
(iii) Salt
(iv) Water
(v) Hydrogen

51. Match the following: 

Column A	Column B
1. Acid salt 2. Mixed salt 3. Complex salt 4. Double salt 5. Normal salt	a. Sodium potassium carbonate b. Alum c. Sodium carbonate d. Sodium zincate e. Sodium hydrogen carbonate

Answer 

Column A	Column B
1. Acid salt 2. Mixed salt 3. Complex salt 4. Double salt 5. Normal salt	e. Sodium hydrogen carbonate a. Sodium potassium carbonate d. Sodium zincate b. Alum c. Sodium carbonate

52. What are the terms defined in (i) and (ii) below?
(i) A salt containing a metal ion surrounded by other ions or molecules.
(ii) A base which is soluble in water.

(i) Complex salt.
(ii) Alkali.

53. Choose the correct answer:
Carbon dioxide and sulphur dioxide gas can be distinguished by using:
(a) Moist blue litmus paper.
(b) Lime water
(c) Acidified potassium dichromate paper
(d) None of the above.

Answer 

Acidified potassium dichromate paper

54. Solution A is a strong acid.
Solution B is a weak acid.
Solution C is a strong alkali.
(i) Which solution contains solute molecules in addition to water molecules?
(ii) Which solution will give a gelatinous white precipitate with zinc sulphate solution? The precipitate disappears when an excess of the solution is added.
(iii) Which solution could be a solution of glacial acetic acid?
(iv) Give an example of a solution which is a weak alkali.

Answer 

(i) Solution B.
(ii) Solution A.
(iii) Solution B
(iv) Solution of ammonium hydroxide NH₄OH is a weak alkali.

55. (a) The diagram given below is to prepare iron (III) chloride in the laboratory : 

(i) What is substance B ?
(ii) What is the purpose of B?
(iii) Why is iron (III) chloride to be stored in a closed container ?
(iv) Write the equation for the reaction between iron and chloride?
(b) Write the equations for the reaction to prepare lead sulphate from lead carbonate ? 

Answer

(a) (i) Substance B is a dehydrating agent. 
(ii) B prevents the entry of moisture inside the apparatus because it absorbs moisture.
(iii) Iron (III) chloride is stored in a closed container because it is a deliquescent compound. 
(iv) 2Fe + 3Cl₂ ⟶ 2FeCl₃ 
(b) PbCO₃ + 2HNO₃ ⟶ Pb(NO₃)₂ + H₂O + CO₂ 
Pb(NO₃)₂ + H₂SO₄ ⟶ PbSO₄  + 2HNO₃

56. Select the correct answer from the choices a,b,c and d which are given.
Write only the letter corresponding to the correct answer.
(i) A particular solution contains molecules and ions of the solute so it is a
(a) Weak acid
(b) Strong acid
(c) Strong base
(d) Salt solution

(ii) An organic weak acid is
(a) Formic acid
(b) Sulphuric acid
(c) Sulphuric base
(d) Hydrochloric acid

(iii) An example of a complex salt is
(a) Zinc sulphate
(b) Solution hydrogen sulphate
(c) Iron(II) ammonium sulphate
(d) Tetramine copper (II) sulphate

Answer 

(i) A
(ii) A
(iii) D

57. Write the equation for the following reaction:
Magnesium sulphate solution is mixed with barium chloride solution.

Answer 

MgSO₄ + BaCl₂ ⟶ BaSO₄ + MgCl₂ 

58. Give the equation for the preparation of each of the following salts from the starting material given.
(i) Copper sulphate from copper (II) oxide
(ii) Iron (III) Chloride from Iron
(iii) Potassium sulphate from potassium hydroxide solution
(iv) Lead chloride from lead carbonate (two equations)

Answer 

(i) CuO + H₂SO₄ → CuSO₄ + H₂O
(ii) 2Fe + 3Cl₂ → 2FeCl₃
(iii) 2KOH + H₂SO₄ → K₂SO₄ + 2H₂O
(iv) PbCO₃ + 2HNO₃ → Pb(NO₃)₂ + H₂O + CO₂
Pb(NO₃)₂ + 2NaCl → PbCl₂ + 2NaNO₃ 

59. Solution A is a sodium hydroxide solution. Solution B is a weak acid. Solution C is dilute sulphuric acid. Which solution will.
(i) Liberate sulphur dioxide from sodium sulphite
(ii) Give a white precipitate with zinc sulphate solution,
(iii) Contain solute molecules and ions?

Answer 

(i) C = Dilute sulphuric acid
(ii) A = Sodium hydroxide
(iii) B = Weak acid

60. What happen to the crystals of washing soda when exposed to air? Name the phenomenon exhibited.

Answer 

When crystals of washing soda are exposed to air, it loses its water of crystallisation and the phenomenon is known as efflorescence.

61. Name the method used for preparation of the following salts from the list given below:
(i) Sodium nitrate
(ii) Iron (III) chloride
(iii) Lead chloride
(iv) Zinc sulphate
(v) Sodium hydrogen sulphate
List :
(a) Simple displacement
(b) Neutralization
(c) Decomposition by acid
(d) Double decomposition
(e) Direct synthesis

Answer 

(i) (B) Neutralisation
(ii) (E) Direct synthesis
(iii) (D) Double decomposition
(iv) (A) Simple displacement
(v) (C) Decomposition by acid

62. From the list given below, select the word(s) required to correctly complete blanks (i) to (v) in the following passage. The words from the list are to be used only once. Write the answers as (a) (i), (ii) (iii) and so on. Do not copy the passage
Ammonia, ammonium, carbonate, carbon dioxide, hydrogen, hydronium, hydroxide, precipitate, salt, water
(a) A solution M turns blue litmus red, so it must contain (i) _______ ions; another, solution O turns red litmus blue and hence, must contain (ii)__________ ions
(b) When Solutions M and O are mixed together, the products will be (iii) ________ and (iv) ________
(c) If a piece of magnesium was put into a solution M.(v) _________________Gas would be evolved

Answer 

(i) Hydronium
(ii) Hydroxide
(iii) Salt
(iv) Water
(v) Hydrogen

63. State what would you observe when :
(a) Washing soda crystals are exposed to the atmosphere.
(b) The salt ferric chloride is exposed to the atmosphere.

Answer 

(a) When washing soda (Na₂CO₃.10H₂O) is exposed to air, it loses 9 molecules of water to form a monohydrate.

(b) It absorbs moisture from the atmosphere and becomes moist and ultimately dissolves in the absorbed water, forming a saturated solution.

64. Match the salts given in Column I with their method of preparation given in Column II:

Column I	Column II
(i) P(NO3)2 from PbO (ii) MgCl2 from Mg (iii) FeCl3 from Fe (iv) NaNO3 from NaOH (v) ZnCO3 from ZnSO4	(A) Simple displacement (B) Titration (C) Neutralisation (D) Precipitation (E) Combination

Answer 

Column I	Column II
(i) P(NO3)2 from PbO (ii) MgCl2 from Mg (iii) FeCl3 from Fe (iv) NaNO3 from NaOH (v) ZnCO3 from ZnSO4	(A) Precipitation (F) Simple displacement (B) Combination (G) Neutralisation (H) Titration

65. Fill in the blank from the choices given in bracket:
(a) When a metallic oxide is dissolved in water, the solution formed has a high concentration of _______ ions. (H⁺,H₃O⁺,OH^-)

Answer

(a) When a metallic oxide is dissolved in water, the solution formed has a high concentration of OH⁻ ions.

66. To increase the pH value of neutral solution, we should add
(a) An acid
(b) An acid salt
(c) An alkali
(d) A salt

Answer  

(b) (c) An alkali