Students of ICSE Class 10 should refer to Study of Acids, Bases and Salts ICSE Class 10 Chemistry board year questions and solutions. below which have come in past board exams. You should always go through questions that have come in previous years. This will help you to understand the pattern of questions in ICSE Class 10 Chemistry and prepare accordingly. This will help you to get better marks in ICSE Class 10 Board Exams
ICSE Class 10 Chemistry Study of Acids, Bases and Salts Board Exam Questions
Students should learn the important questions and answers given below for Chapter Study of Acids, Bases and Salts in Chemistry for ICSE Class 10. These board questions are expected to come in the upcoming exams. Students of ICSE Class 10th should go through the below board exams questions and answers which will help them to get more marks in exams.
Board Exam Questions Study of Acids, Bases and Salts ICSE Class 10 Chemistry
Question: Salts of strong acids and strong bases in water produce (1) ……………solution. Solution of sodium carbonate in water is (2) ………………..in nature, while the solution of ferric chloride is (3) ………………in nature.
(1) Neutral, (2) basic, (3) acidic.
Question: A solution X turns blue litmus red, so it must contain :
(1) ………ions. Another solution Y turns red litmus blue and therefore, must contain
(2) ………ions. When solutions X and Y are mixed together, the products will be a (3)…… and
(4) ………. If a piece of magnesium was put into solution X. (5) ……… gas would be evolved.
(1) hydronium, (2) hydroxide, (3) salt, (4) water, (5) hydrogen.
Question: In making copper sulphate crystals, a black powder called (1) ………… is added to dilute (2) ……… acid and the mixture is warmed. Excess black powder is added to a small volume of acid so as to (3) ……….. The excess insoluble black powder is got rid by (4) ……… The resulting clear solution looks (5) ……….. in colour. This solution is heated to get rid of some of the (6)……….. Slow cooling of the remaining solution (7) …………. of pure copper sulphate.
(1) Copper oxide, (2) Sulphuric, (3) neutralise the excess of the acid, (4) filtration, (5) blue, (6)
copper sulphide as impurity, (7) gives well-defined crystals.
Question: Deliquescence takes place because of the difference in (1) …………………………of atmospheric (2) ……………..and that of the deliquescent substance. The vapour pressure of atmospheric humidity is (3) ………than that of the deliquescent substance. The substances which take up water on exposure to atmosphere, without forming a solution are known as (4) …………….. substances.
Ans. (1) vapour pressure, (2) humidity, (3) higher, (4) hygroscopic.
(e) Question.. An acid is a compound which when dissolved in water gives ………………….. ions as the only ……………….. ions.
Question. A ………………….. acid undergoes almost complete dissociation on dissolving in water.
Question. An example of mineral acid is ……………………
Question. Vinegar contains ………………….. acid.
Question. Sodium acetate on hydrolysis forms sodium hydroxide and ………………….. .
Question. The basicity of Acetic Acid is ………….
Question. Metal A reacts with cold water forming hydrogen and new compound B. The anion combined with A in a substance B is named ………………. .
Question. The solution of sodium carbonate is alkaline due to ……………………….. .
Question. The complete reaction between an acid and a base is called ………………… .
Question. The pH value of a neutral solution is …………………………… .
Question. As the pH of solution decreases, its acidic strength progressively ………….. .
Question. As the pH of solution increases, the ………………….. strength of the solution progressively decreases.
Question. pH value of lemon juice is ……………… than 7.
Question. Ammonium hydroxide is a ……………. base.
Question. Methyl orange turns …………………… in acidic solution.
Question. The formation of a salt from an acid and a base involves the combination of………………. from the acid and the……………….from the………………..to form………………….. molecules.
H+, OH–, base, water
Question. A salt which absorbs moisture from the air, but does not change in physical state in called ……………….. salt.
Question. Ammonium chloride is a ………………….. salt.
Question. Sodium hydrogen sulphate is ……………. salt.
Question. The salt of the acid HNO2 are called…………………..and those of the acid HNO3 are called ………………… .
Question. Sodium sulphite reacts with dilute sulphuric acid to form sodium sulphate …………….. gas and water.
Question. Copper (II) chloride reacts with sodium hydroxide to form …………………. copper hydroxide and sodium chloride.
Question. A chemical reaction between hydronium ions of an acid and OH– ions of a base to form unionised water is called ……………………… .
Question. Dissolving of aluminium foil in HCl as well as NaOH shows that it is ……………. in nature.
Question. An example of a deliquescent salt is ……………………..
Question. Superphosphate is an example of a compound called………… .
Question. The number of H+ ions of an acid which react completely with one molecule of a base is called its …………. .
Question. When a metallic oxide is dissolved in water, the solution formed has high concentration of……………ions.
Question. The metal which does not react with water or dilute H2SO4 but reacts with concentrated H2SO4 is…………….
Question. The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction………….
Question. The divalent metal whose oxide is reduced to metal by electrolysis of its fused saltis………….
Question. Higher the pH value of a solution, the more…………it is.
Multiple Choice Questions
Question. 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
Question. Select the acid which contains four hydrogen atoms in it :
(a) Formic acid
(b) Sulphuric acid
(c) Nitric acid
(d) Acetic acid
Question. An organic weak acid is :
(a) Formic acid
(b) Sulphuric acid
(c) Nitric acid
(d) Hydrochloric acid
Question. The aqueous solution of the following compounds which contains both ions and molecules is :
(a) Sulphuric acid
(b) Hydrochloric acid
(c) Nitric acid
(d) Acetic acid
Question. An acid which is not a hydro acid is :
Question. Which one of the following will not produce an acid when made to react with water ?
(a) Carbon monoxide
(b) Carbon dioxide
(c) Nitrogen dioxide
(d) Sulphur trioxide
Question. The metal oxide which can react with acid as well as alkali is :
(a) Silver oxide
(b) Copper (II) oxide
(c) Aluminium oxide
(d) Calcium oxide
Question. During ionization metals lose electrons, this change can be called :
Question. The salt which in solution gives a pale green precipitate with sodium hydroxide solution and a white precipitate with barium chloride solution is :
(a) Iron (III) sulphate
(b) Iron (II) sulphate
(c) Iron (II) chloride
(d) Iron (III) chloride
Question. An example of a complex salt is :
(a) Zinc sulphate
(b) Sodium hydrogensulphate
(c) Iron (II) ammonium sulphate
(d) Tetrammine copper (II) sulphate
Question. To increase the pH value of neutral solution, we should add :
(a) An acid
(b) An acid salt
(c) An alkali
(d) A salt
Give One Word/Chemical Term
Question. Name the acids, which are used in food stuffs.
Citric acid, tartaric acid and acetic acid
Question. Two monobasic acids containing nitrogen.
Nitric acid and nitrous acid
Question. Two dibasic acids containing sulphur.
Sulphuric acid and sulphurous acid
Question. Strong acid containing chlorine.
Question. Two gases–one of which is basic and which combine to give a solid
Ammonia and hydrogen chloride
Question. Basic anhydride of calcium hydroxide.
Question. Product obtained when lime water dries up.
Calcium oxide and carbon dioxide
Question. Three common indicators to indicate presence of acids and alkalies.
Litmus, methyl orange, phenolphthalein
Question. This gas turns moist lead acetate paper black.
Question. The compound which is responsible for the green colouration when sulphur dioxide is passed through acidified potassium dichromate solution.
Question. The compound responsible for the brown ring during the brown ring test of nitrate ion.
Nitroso Iron (II) sulphate
Question. A salt formed by incomplete neutralisation of an acid by a base.
Question. This salt gives nitrogen dioxide on heating.
Question. This compound is an acid salt.
Question. On heating, this salt changes from green to black.
Question. On treating with concentrated sulphuric acid, this salt changes from blue to white.
Question. A compound which is insoluble in cold water, but soluble in hot water.
Lead (II) chloride
Question. A compound whose aqueous solution is neutral in nature.
Question. Three metals that can form bases when treated with water.
Sodium, calcium and potassium
Question. Acid anhydride of sulphuric acid.
Question. The process in which a substance absorbs moisture from the atmospheric air to become moist, and ultimately dissolves in the absorbed water.
Question. A compound which is deliquescent.
Caustic Soda (NaOH)
Question. Name an acidic hygroscopic substance.
Sulphuric acid, or oil of vitriol
Question. Name a basic hygroscopic substance.
Question. Name any two efflorescent substances.
Copper sulphate (Blue vitriol) and Washing soda (Sodium carbonate)
Define/Explain the Following
1. An acid
A compound which on dissolving in water furnishes a proton [Hydrogen ion (H+)] as the only positively charged ion is called acid or it is a compound which dissolves in water to
form hydronium ion, i.e., HCl, H2SO4 etc.
2. A base
A base is a compound which combines with the hydronium ion (H3O+) of an acid to form salt and water only, or it is the oxide or hydroxide of a metal which will neutralize the acid.
3. An alkali
An alkali is a compound, which on dissolving in water furnishes OH– ions as only negative ions, e.g., NaOH, KOH etc. The soluble bases are called alkali.
A salt is an ionic compound which when dissolved in water, yields a positive ion other than hydrogen ion (H+) and a negative ion other than hydroxyl ion (OH–).
5. Normal salt
A normal salt is one which does not contain any of ionisable or replaceable hydrogen atoms in its molecule. For example : NaCl, Na2SO4, AgCl, FeCl3 etc.
6. Acid salt
An acid salt contains one or more partially replaceable hydrogen ions (H+) in it. For example : NaHCO3, KHSO3, Ca(HCO3)2 etc.
7. Basic salt
A basic salt is formed as a result of incomplete neutralisation of a base by an acid. It contains replaceable hydroxyl ions (OH–). For example : CuCO3, Cu(OH)2, PbCO3, Pb(OH)2 etc.
Balancing/Writing the Chemical Equations
(a) Write correctly balanced equations for the following reactions :
1. Molten sodium and chlorine.
1. 2Na + Cl2 ⎯⎯→ 2NaCl
2. Nitrogen and oxygen, when lightning strikes.
2. N2 + O2 ⎯⎯→ 2NO
3. Iron and dilute sulphuric acid.
3. Fe + H2SO4 ⎯⎯→ FeSO4 + H2
4. Decomposition of hypochlorous acid in sunlight.
5. Decomposition of potassium nitrate.
5. 2KNO3 ⎯⎯→ 2KNO2 + O2
6. Sodium thiosulphate is reacted with dilute hydrochloric acid.
6. Na2S2O3 + 2HCl ⎯→ 2NaCl + SO2 + + S ↓ + H2O
7. Calcium bicarbonate reacts with dilute hydrochloric acid.
7. Ca(HCO3)2 + 2HCl ⎯→ CaCl2 + 2H2O + 2CO2 ↑
8. Dilute sulphuric acid is poured over sodium sulphate.
8. Na2SO3 + H2SO4 (dilute) ⎯→ Na2SO4 + H2O + SO2 ↑
9. Lead nitrate solution is added to sodium chloride solution.
9. Pb(NO3)2 + 2NaCl ⎯→ PbCl2 + 2NaNO3
10. Zinc is heated with sodium hydroxide solution.
10. Zn + 2NaOH ⎯→ Na2ZnO2 + H2 ↑
11. Lead sulphate from lead nitrate solution and dilute sulphuric acid.
11. Pb(NO3)2 + H2SO4 ⎯→ PbSO4 ↓ + 2HNO3
Lead Sulphuric Lead Nitric acid
nitrate acid sulphate
12. Copper sulphate from copper and concentrated sulphuric acid.
- Cu + 2H2SO4 ⎯→ CuSO4 + 2H2O + SO2
Copper Sulphuric Copper Water Sulphur
acid sulphate dioxide
13. Lead chloride from lead nitrate solution and sodium chloride solution.
- Pb(NO3)2 + 2NaCl ⎯→ PbCl2 + 2NaNO3
Lead Sodium Lead Sodium
nitrate chloride chloride nitrate
14. Ammonium sulphate from ammonia and dilute sulphuric acid.
14. 2NH3 + H2SO4 ⎯→ (NH4)2SO4
Ammonia Sulphuric Ammonium
15. Sodium chloride from sodium carbonate solution and dilute hydrochloric acid.
15. Na2CO3 + 2HCl ⎯→ NaCl + H2O + CO2
Sodium Hydrochloric Sodium Water Carbon
carbonate acid chloride dioxide
16. Magnesium and dilute sulphuric acid.
16. MgO + H2SO4 (dil.) ⎯→ MgSO4 + H2↑
17. Zinc carbonate and dilute sulphuric acid.
17. ZnCO3 + H2SO4 ⎯→ ZnSO4 + H2O + CO2 ↑
18. Copper oxide and dilute sulphuric acid.
18. CuO + H2SO4 (dil.) ⎯→ CuSO4 + H2O
19. Ferric hydroxide reacts with nitric acid.
19. Fe(OH)3 + 3HNO3 ⎯→ Fe(NO3)3 + 3H2O
20. Zinc oxide dissolves in sodium hydroxide.
20. ZnO + 2NaOH ⎯→ Na2ZnO2 + H2O
(b) Write the equation for the laboratory preparation of the following salts.
1. Iron(II) sulphate from iron.
2. Copper sulphate from copper.
3. Lead sulphate from lead nitrate.
4. Sodium sulphate from sodium carbonate.
Na2CO3 + H2SO4 ⎯→ Na2SO4 + H2O + CO2
5. Copper sulphate from copper(II) oxide.
- CuO + H2SO4 ⎯→ CuSO4 + H2O
Copper(II) oxide Copper
6. Iron(III) chloride from iron.
- 2Fe + 3Cl2 ⎯→ 2FeCl3
Iron Chlorine Ferric chloride
7. Potassium sulphate from potassium hydroxide solution.
8. Lead chloride from lead carbonate (two equations).
9. Zinc sulphate from zinc.
9. Zn + H2SO4 ⎯→ ZnSO4 + H2 ↑
10. Sodium sulphate from sodium hydroxide.
10. 2NaOH + H2SO4 ⎯→ Na2SO4 + 2H2O
11. Lead(II) chloride from lead nitrate.
Pb (NO3)2 + 2HCl ⎯→ PbCl2 + 2HNO3
12. Copper(II) sulphate from copper carbonate.
- CuCO3 + H2SO4 ⎯→ CuSO4 + H2O + CO2
Copper (dil.) Copper(II)
13. Calcium carbonate from calcium chloride.
CaCl2 + Na2CO3 ⎯→ CaCO3 + 2NaCl
14. Sodium sulphate from sodium carbonate.
- Na2CO3 + H2SO4 ⎯→ Na2SO4 + H2O + CO2
Sodium dil. Sodium
carbonate sulphuric acid sulphate
15. Zinc carbonate from zinc nitrate.
- Zn(NO3)2 + Na2CO3 ⎯→ ZnCO3 + 2NaNO3
Zinc nitrate Sodium Zinc Sodium
carbonate carbonate nitrate
(c) Study the following conversion schemes :
1. Give the equations for the following conversions A to E.
2. Refer to the flow chart diagram below and give balanced equations with conditions, if any, for the following conversions A to D.
(i) For each of the conversions A to D in the above state briefly how the conversions can be carried out.
(ii) Write equations for the conversions.
4. For each of the conversion in the scheme given below, state briefly in words or by means of chemical equation, how the conversion is carried out ?
5. How are the following conversions carried out ? Give balanced chemical equations only.
[B] Lead(II) oxide, when dissolved in the dilute nitric acid, lead nitrate is formed.
[A] Lead(II) oxide, when heated with powdered coke, reduced to metallic lead and carbon monoxide is formed.
PbO + C ⎯→ Pb + CO
PbO + 2HNO3 ⎯→ Pb(NO3)2 + H2O
Lead nitrate [C] Lead(II) nitrate is dissolved in water and then sodium hydroxide solution is added, a white precipitate of lead hydroxide is obtained.
Pb(NO3)2 + 2NaOH ⎯→ Pb(OH)2 + 2NaNO3 [D] Lead(II) nitrate is dissolved in water and then concentrated solution of sodium carbonate is added, a white precipitate of lead (II) carbonate is obtained.
Pb(NO3)2 + Na2CO3 ⎯→ PbCO3 + 2NaNO3 [A] Copper(II) oxide, when heated with coke powder is reduced to metallic copper.
CuO + C ⎯→ Cu + CO
Metallic copper [B] Copper(II) oxide is dissolved in dilute sulphuric acid to form copper sulphate.
CuO + H2SO4 ⎯→ CuSO4 + H2O
sulphate [C] Copper sulphate is dissolved in water and hydrogen sulphide gas is passed, a black precipitate of copper sulphide is formed.
CuSO4 + H2S ⎯→ CuS + H2SO4
Black ppt. [D] Copper(II) oxide is dissolved in dilute hydrochloric acid to form copper chloride. To the solution of copper chloride, when a saturated solution of sodium carbonate is added, a light blue precipitate of copper(II) carbonate is formed.
CuCl2 + Na2CO3 ⎯→ CuCO3 + 2NaCl
(d) How can the following be converted to the respective chloride, sulphate and nitrate salts ? Give equations :
1. Magnesium, 2. Zinc, 3. Iron, 4. Lead carbonate, 5. Copper oxide, 6. Potassium hydroxide, 7. Copper hydroxide, 8. Ammonium hydroxide.
Ans. (i) CaCO3 + 2HCl ⎯→ CaCl2 + H2O + CO2
(ii) NaHCO3 + HNO3 ⎯→ NaNO3 + H2O + CO2
(iii) ZnSO3 + 2HCl ⎯→ ZnCl2 + H2O + SO2
(iv) 2KHSO3 + H2SO4 ⎯→ K2SO4 + 2H2O + 2SO2
Q. How will you distinguish between the following pairs of compounds :
1. Iron(II) chloride and Iron(III) chloride.
Iron(II) chloride is dissolved in water and then sodium hydroxide is added. A dirty green precipitate is obtained which confirms the presence of iron(II) chloride.
FeCl2 + 2NaOH ⎯→ Fe(OH)2 + 2NaCl
Iron(III) chloride is also dissolved in water and then sodium hydroxide solution is added. A reddish brown precipitate is obtained, which confirms the presence of iron(III) chloride.
FeCl3 + 3NaOH ⎯→ Fe(OH)3 + 3NaCl
2. Lead nitrate and copper nitrate.
Lead nitrate is dissolved in water and then sodium hydroxide solution is added, a white precipitate is obtained, which is soluble in excess of sodium hydroxide.
Pb(NO3)2 + 2NaOH ⎯→ Pb(OH)2 + 2NaNO3
Copper nitrate is dissolved in water and sodium hydroxide solution is added, a light blue precipitate of copper hydroxide is obtained.
Cu(NO3)2 + 2NaOH ⎯→ Cu(OH)2 + 2NaNO3
3. Zinc oxide and calcium oxide.
Zinc oxide is dissolved in dilute hydrochloric acid to form zinc chloride and then sodium hydroxide solution is added, a white precipitate is obtained, which is soluble in excess of
sodium hydroxide to form a clear solution.
ZnO + 2HCl ⎯→ ZnCl2 + H2O
ZnCl2 + 2NaOH ⎯→ Zn(OH)2 + 2NaCl
Zn(OH)2 + 2NaOH ⎯→ Na2ZnO2 + 2H2O
(A clear solution)
Calcium chloride is obtained by dissolving calcium oxide in dilute hydrochloric acid. To the solution of calcium chloride, sodium hydroxide solution is added, a white precipitate of
calcium hydroxide is obtained, which is insoluble even in the excess of sodium hydroxide.
CaO + 2HCl ⎯→ CaCl2 + H2O
CaCl2 + 2NaOH ⎯→ Ca(OH)2 + 2NaCl
4. Sodium carbonate and sodium nitrate.
Sodium carbonate when treated with dilute hydrochloric acid, a vigorous reaction takes place and a colourless, odourless gas carbon dioxide is evolved which turns lime water milky.
Na2CO3 + 2HCl ⎯→ 2NaCl + H2O + CO2
Sodium nitrate when mixed with copper filings and heated with concentrated sulphuric acid, reddish brown fumes of nitrogen dioxide are evolved.
2NaNO3 + H2SO4 ⎯→ Na2SO4 + 2HNO3
Cu + 4HNO3 ⎯→ Cu(NO3)2+ 2NO2+ 2H2O
5. Sodium sulphate and sodium sulphite.
Sodium sulphate is dissolved in water and barium chloride solution is added, an insoluble white precipitate of barium sulphate is obtained.
Na2SO4 + BaCl2 ⎯→ BaSO4 + 2NaCl
Sodium sulphite is warmed with dilute sulphuric acid, a colourless gas with a pungent and suffocating smell is evolved. When this gas is bubbled through acidified solution of potassium dichromate, it turns its colour from orange to green.
Na2SO3 + H2SO4 ⎯→ Na2SO4 + H2O + SO2
K2Cr2O7 + H2SO4 + 3SO2 ⎯→ K2SO4 + Cr2(SO4)3 + H2O
6. How will you distinguish between ammonium hydroxide and sodium hydroxide using copper sulphate solution ?
When ammonium hydroxide solution is added drop by drop to copper sulphate solution, a pale blue or bluish white precipitate is formed which is soluble in excess of ammonium
hydroxide and a deep blue or inky blue solution is formed with excess of ammonium hydroxide.
CuSO4 + 2NH4OH ⎯→ Cu(OH)2 + (NH4)2SO4
Cu(OH)2 + 4NH4OH ⎯→ [Cu(NH3)4](OH)2 + 4H2O
Copper solution forms a blue precipitate with sodium hydroxide solution. It is insoluble in excess of NaOH.
CuSO4 + 2NaOH ⎯→ Cu(OH)2 + Na2SO4
Copper Sodium Copper Sodium
sulphate hydroxide hydroxide sulphate
Reasoning Based Questions
Q. 1. Hydrochloric acid is considered as a strong acid whereas acetic acid is a weak acid. Why ?
Hydrochloric acid is considered as a strong acid because it dissociates completely in water.
HCl (aq.) ⇌ H+ (aq.) + Cl– (aq.)
Acetic acid is a weak acid as it dissociates partially when dissolved in water. Most of its molecules remain in molecular form in the solution.
CH3COOH (aq) ⇌ CH3COO– (aq) + H+ (aq)
Q. 2. Why dilute sulphuric acid is stronger acid than concentrated sulphuric acid ?
The presence of water in dilute sulphuric acid increases the hydrogen ion concentration. Hence it is a stronger acid than concentrated sulphuric acid which contains comparatively less water.
Q. 3. Acetic acid is monobasic. Why ?
Acetic acid is monobasic because it has one ionisable hydrogen ion and combines with one hydroxyl ion of the base to give a single salt and water.
CH3COOH ⇌ CH3COO– + H+
NaOH + CH3COOH ⎯⎯→ CH3COONa + H2O
Q. 4. Carbonic acid is a dibasic acid. Why ?
Carbonic acid (H2CO3) is a dibasic acid because it has two replaceable hydrogen atoms and hence it combines with two hydroxyl groups of the bases to form two kinds of salt and water.
H2CO3 ⇌ HCO3– + H+
HCO3 ⇌ CO32– + H+
The displacement of two hydrogen atoms takes place in two steps.
Q. 5. Sodium hydroxide is a monoacidic base. Why ?
Sodium hydroxide is a mono-acidic base as it combines with only one hydrogen ion.
NaOH (aq) + HCl (aq) ⎯→ NaCl (aq) + H2O (l)
Q. 6. An aqueous solution of the salt ammonium chloride is acidic in nature while an aqueous solution of sodium chloride is neutral. Why ?
Ammonium chloride is a salt of weak base and strong acid, it undergoes salt hydrolysis to produce an acidic solution whereas sodium chloride is a salt of strong acid and strong base, it does not undergo salt hydrolysis hence its solution remains neutral.
Q. 7. An aqueous solution of the zinc sulphate is acidic in nature. Why ?
When zinc sulphate is dissolved in water, it is hydrolysed to form sulphuric acid and zinc hydroxide. Sulphuric acid is a strong acid, while zinc hydroxide is a weak base, hence, the solution is acidic in nature.
ZnSO4 + 2H2O ⎯→ Zn(OH)2 + H2SO4
Weak base Strong acid
Q. 8. An aqueous solution of ammonium acetate is neutral in nature. Why ?
Ammonium acetate, when dissolved in water is hydrolysed to form ammonium hydroxide and acetic acid. Ammonium hydroxide and acetic acid both are weak alkali and acid respectively, hence the solution is neutral in nature.
Q. 9. An aqueous solution of sodium carbonate is alkaline and that of ammonium chloride is acidic in behaviour. Why ?
An aqueous solution of sodium carbonate is alkaline and that of ammonium chloride is acidic in behaviour. Why ?
Ans. Both of these salts react with water. Sodium carbonate reacts with water, producing a strong alkali, sodium hydroxide and a weak acid, carbonic acid. Hence, the solution is alkaline :
Na2CO3 + H2 ⇌ 2NaOH + H2CO3
Ammonium chloride reacts with water to produce ammonium hydroxide, a weak alkali and hydrochloric acid, a strong acid. Hence the solution is acidic :
NH4Cl + H2 ⇌ NH4OH + HCl
Q. 10. A universal indicator is more meaningful than an ordinary indicator.
A universal indicator is better than an ordinary indicator as it not only shows whether the solution is acidic or basic but also gives the pH values (approx.) by giving a wide range of colours corresponding to different pH values.
Q. 1. 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 could be a solution of glacial acetic acid ?
(iii) Give an example of a solution which is a weak alkali.
(i) B (ii) B (iii) Ammonium hydroxide
Q. 2. (i) What is basicity of an acid. Give examples.
(ii) Give the basicity of nitric acid, acetic acid and phosphoric acid.
(iii) State two properties of an acid.
(iv) On what factors the strength of an acid depend ?
(v) Name an acid used : (a) as a flavour and to preserve food, (b) in a drink, (c) to remove ink spots, (d) as an eye wash.
(i) The number of replaceable hydrogen atoms, present in one molecule of an acid is known as basicity of the acid. For example hydrochloric acid is a monobasic acid, sulphuric acid is a dibasic acid and phosphoric acid is a tribasic acid.
(ii) Nitric acid (HNO3) ⎯→ Monobasic
Acetic acid (CH3COOH) ⎯→ Monobasic
Phosphoric acid (H3PO4) ⎯→ Tribasic.
(iii) (a) An acid turns methyl orange into pink and blue litmus to red.
(b) An acid with a base forms salt and water only.
NaOH + HCl ⎯→ NaCl + H2O
(Alkali) (Acid) (Salt) (Water)
(iv) The strength of an acid depends on the following factors :
(a) Reactivity of the acid.
(b) Degree of ionisation to H+ ion.
(v) (a) Citric acid. (b) Carbonic acid.
(c) Oxalic acid. (d) Boric acid.
Q. 3. (i) What is acidity of a base. Give examples.
(ii) State three properties of an alkali.
(i) The number of hydroxyl ions that one molecule of a base gives on dissociation is known as acidity of a base. e.g., The acidity of sodium hydroxide (NaOH) is one, it is a monoacid, the acidity of Ca(OH)2 is two, it is a diacid base, Al(OH)3 is a triacid base.
(ii) An alkali turns :
(a) Red litmus blue (b) Phenolphthalein to pink (c) Methyl orange to yellow.
Q. 4. Name the kind of particles present in :
(i) Sodium hydroxide solution. (ii) Carbonic acid (iii) Sugar solution.
(i) Sodium ions and hydroxide ions.
(ii) Carbonic acid molecules, carbonate ions and hydronium ions.
(iii) Sugar molecules and water molecules.
Q. 5. 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.
(i) C (ii) A (iii) B
Q. 6. (i) What are indicators ?
(ii) Name three indicators and their colours in different medium.
(iii) What is reaction of neutralization ?
(iv) Give two practical application of neutralization.
(i) Indicators are complex organic compounds, which are used to distinguish between acidic and alkaline solutions by the abrupt change in their colour, e.g. litmus, methyl orange and phenolpthalein.
Q. 7. (i) Explain pH value of a solution.
(ii) What is the pH of :
(a) Pure water (b) Milk (c) Human blood
(iii) The pH value of three solutions is given below. Which one of them is acidic, neutral and alkaline in nature ?
(a) pH = 7 (b) pH = 10 (c) pH = 3
(iv) What is pH number assigned to a solution ?
(i) pH value of a solution is the negative logarithm to the base 10 of hydrogen ion concentration expressed in gram-ions per litre.
pH = log10 [H+]
pH value = 7 indicates a neutral solution.
pH value > 7 indicates an alkaline solution.
pH value < 7 indicates an acidic solution.
(ii) The pH of :
(a) Pure water is 7 (b) Milk is 6·6 (c) Human blood is 7·3
(iii) (a) Neutral (b) Alkaline (c) Acidic
(iv) It is a number assigned to express the acidity or alkalinity of a solution which varies from 1b to 14. The pH number less than 7 indicates acidity, while pH number more than 7 indicates alkalinity. The pH of pure water is 7 and it is neutral.
Q. 8. (i) (a) What is the purpose of the pH scale ?
(b) What is the pH of pure water.
(c) A is a soluble acidic oxide, B is a soluble base compared to the pH of pure water, what will be the pH of : (i) a solution of A, (ii) a solution of B.
(ii) Taking sodium carbonate as an example, give the meaning of the following terms :
(a) Water of crystallization (b) Anhydrous (c) Efflorescence.
(i) (a) To measure the degree of acidity or alkalinity.
(b) The pH of pure water is equal to 7.
(c) (i) The pH is less than 7. (ii) The pH is more than 7.
(ii) (a) Water of crystallization is that definite number of water molecules which a crystal contain when it is crystallizing out from an aqueous solution. e.g., Sodium carbonate crystal contains 10 molecules of water i.e., Na2CO3. 10H2O.
(b) When Na2CO3.10H2O is heated, the water of crystallization is evaporated leaving anhydrous sodium carbonate Na2CO3.
(c) The loss of water by a hydrate salt on exposure to air is called efflorescence, e.g.
Na2CO3.10H2O on exposure to air, looses 9 molecules of water of crystallization.
Na2CO3. 10H2O Air⎯⎯→Na2CO3. H2O + 9H2O.
Q. 9. A solution has a pH of 7 explain how you would :
(i) (a) Increase its pH, (b) Decrease its pH.
(ii) If a solution changes the colour of litmus red to blue what can you say about its pH ?
(iii) What can you say about the pH of a solution that liberates carbon dioxide from sodium carbonate.
(i) (a) pH is increased by adding any caustic alkali to solution.
(b) pH is decreased by adding any mineral acid to solution.
(ii) pH of solution is more than 7.
(iii) pH of solution is less than 7.
Q. 10. (i) The pH value is utilised in medicine and agriculture. Explain.
(ii) The pH value of pure water is 7. Compare the pH values of sulphur dioxide solution and ammonia solution with that of pure water.
(iii) How does pH value of a solution and hydrogen ion concentration of solution vary ?
(i) (a) In medicine : The pH values of urine and blood are used to diagnose various diseases.
(b) In agriculture : The pH of soil is checked to ensure fast growth of crops. For example, citrus fruits need slightly alkaline soil, rice crop needs an acidic soil, sugarcane needs a neutral soil.
(ii) Sulphur dioxide is a non-metal oxide, such oxides are acidic with pH less then 7. Ammonia solution is alkaline with pH more than 7.
(iii) Both varies inversely. It is seen that lower the pH value the greater the H+ ion concentration and higher the pH value the lower the H+ ion concentration.