Goyal Brothers Class-10 Acid Base and Salts Ch-3

Goyal Brothers Class-10 Acid Base and Salts Ch-3

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Goyal Brothers Class-10 Acid Base and Salts ICSE Chemistry Solutions Ch-3. Step by Step Solutions of Exercise and Objective Type Questions of Goyal Brothers Prakashan Chapter-3 Chemical Bonding Ionic and Covalent for ICSE Class 10 Chemistry.  Visit official Website CISCE  for detail information about ICSE Board Class-10 Chemistry .

Goyal Brothers Class-10 Acid Base and Salts ICSE Chemistry Solutions Ch-2

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Exercise 1

Exercise 2

Objective Type Questions (update soon)

Exercise 1

 Goyal Brothers Class-10 Acid Base and Salts ICSE Chemistry Solutions Ch-3

Page-48

Question 1. 
(a) What do you understand by the term acid?
(b) Show ionically why (i) phosphoric acid, (ii) sulphuric acid, (ii) acetic acid are called acids?
Answer:
(a)Acid, any substance that in water solution tastes sour, changes the colour of certain indicators (e.g., reddens blue litmus paper), reacts with some metals (e.g., iron) to liberate hydrogen, reacts with bases to form salts, and promotes certain chemical reactions (acid catalysis)
(b)  The main concept of importance is that those substance which gives out hydronium ions or hydrogen ions upon dissociation with water are considered as acids 
 

i) Phosphoric acid:

  • When phosphoric acid is dissociated in the presence of water, the following reaction occurs:

⇔

  • As it gives out hydronium ions, it is called as acids.

ii) Sulfuric acid:

  • When sulfuric acid is dissociated in the presence of water, the following reaction occurs:

  • As it gives out hydronium ions, it is called as acids.

iii) Acetic acid:

  • When acetic acid is dissociated in the presence of water, the following reaction occurs:

⇄

  • As it gives out hydrogen ions, it is called as acids.

Question 2. 

(a) What do you understand by the term “basicity of an acid'”?
(b) Give two examples of (i) monobasic acids (ii) dibasic acids (ii) tribasic acids. Support your answer by ionic equations.
Answer:
(a) Basicity of an acid is the number of hydrogen ions which can be produced by one molecule of acid. e.g. Acetic acid is monobasic in nature as it can lose one proton or hydrogen atom to form acetate ion
(b) two examples of

(i)Monobasic acid- Monobasic acids are acids that furnish only one hydrogen ion (H+) per molecule in water. Example: Hydrochloric acid, nitric acid, acetic acid.

(ii )Dibasic acid- Dibasic acids are acids that furnish two hydrogen ions (H+) per molecule in water. Example: Sulphuric acid, carbonic acid, oxalic acid.

(iii) Tribasic acid- Tribasic acids are acids that furnish three hydrogen ions (H+) per molecule in water. Example: Phosphoric acid, phosphorus acid.

Question 3. Explain why:
(a Sulphuric acid forms two series of salts?
(b) Phosphoric acid forms three series of salts?
Answer:
(a) Explanation: The acids which on dissociation with water yields two hydrogen ions they are called dibasic acids. Sulfuric acid belongs to dibasic acids as it gives two hydrogen ions on dissociation with water. Due to this reason on reaction with strong bases, sulfuric acid forms salts that are neutral
(b ) Phosphoric acid has three hydrogen which can replace with metal atom and form three types of salt. Explanation: Phosphoric acid has three hydrogen which can replace with metal atom and form three types of salt
Question 4. 
(a) What are indicators?
(Page-49)
(b)State colour change, if to a very slightly alkaline solution of the following indicators, is added a few drops of
dilute sulphuric acid
 (i) methyl orange, (ii) phenolphthalein (ii) litmus solution.
Answer:

(a) Those substances which give different colour indifferent medium and thus indicate the presence of acid or base in a solution are called indicators.
Natural indicators : Turmeric, beetroot.
Synthetic indicators : Phenolphthalein and Methyl orange

(b)

(i)Methyl orange: Methyl orange changes to red when added to an acid.

(ii) Phenolphthalein is pink in an alkaline solution but turns colourless in an acidic solution. .

(iii) The main use of litmus is to test whether a solution is acidic or basic. Blue litmus paper turns red under acidic conditions. So sulphuric acid turns blue litmus into red.

Question 5.  Write an equation when an acid reacts with: 
(i) metallic oxide, (ii) metallic hydroxide, (iii) metallic carbonate, (iv) metallic hydrogen carbonate, (v) metallic sulphite, (vi) metallic sulphide, (vii) metallic hydrogen sulphide, (viii) metallic hydrogen sulphite, (ix) a metal higher in metal activity series than hydrogen.
Answer:
 refer to page-41 (full page)
Question 6. Dilute HCl and Sulfuric acid react with metals above hydrogen in the metal activity series to liberate hydrogen gas. However,
nitric acid liberates oxides of nitrogen. Explain, by giving two examples along with fully balanced equations.
Answer:

Reaction of metals with dilute acids

Metals usually displace hydrogen from dilute acids.

Less reactive metal(Cu,Au,Ag) do not displace hydrogen from dilute acid.

2Na+2HCl——>2NaCl + hydrogen (react violently)

Mg(s) + + 2 HCl (aq) —–> MgCl2 (aq) + H2 (g)

Al(s) + 6 HCl (aq) —-> AlCl3 (aq) + 3 H2 (g)

Zn(s) + 2 HCl (aq) —-> ZnCl2  (aq) + H2 (g)

Fe (s) + 2 HCl (aq) —-> FeCl2  (aq) + H2 (g)

Silver and gold do not react with dilute acids.

The metals like Cu,Au,Ag are less reactive than hydrogen.They do not displace hydrogen from dilute acids.

Those metals which are above in the reactivity series displace hydrogen from dilute acids.

2Na (s) + H2SO4  (aq) ——> Na2SO4 (aq) + H2 (g)

Mg (s) + H2SO4  (aq) ——> MgSO4 (aq) + H2 (g)

2Al (s) + 3 H2SO4  (aq) ——> Al2(SO4)3 (aq) + H2 (g)

Zn(s) + H2SO4  (aq) ——>  ZnSO4 (aq) + H2 (g)

Cu (s) + H2SO4  (aq) ——>  no reaction

When a metal react with dilute nitric acid,then hydrogen gas is not evolved.Nitric acid is a strong oxidising agent.As soon as hydrogen gas is formed in reaction between metal and dilute nitric acid,the nitric acid oxidises this hydrogen to water.Nitric acid itself is reduced to nitrogen oxides such
as nitrogen monoxide,dinitrogen monoxide.
The arrangement of metals in decreasing order of their reactivities is called reactivity series or activity series of metals.

Question 7.
(a) What do you understand by the term “acidity of a base”?
(b) Give two examples of (i) monoacidic base (ii) diacidic base (iii) triacidic base.
(c) Which of the bases you have mentioned in (b) are alkalis and why?
Answer:

 (a)  Acidity of base. Number of replaceable Hydroxyl groups present in one molecule of base is known as acidity of a base.

(b) Give two examples of
(i) monoacidic base  – Number of replaceable OH groups present in one molecule of a base i.e for NaOH, the acidity is 1
(ii) diacid base–Diacidic base: Diacidic base furnish two hydroxyl ions (OH–) per molecule in water. Example:Calcium hydroxide, copper (II) hydroxide.
 (iii) triacid base.–Triacaidic base: Triacaidic base furnish three two hydroxyl ions (OH–) per molecule in water. Example: Aluminium hydroxide, ferric hydroxide.
(c)  the bases  mentioned in (b) are alkalis  because the are soluble in water
Question 8.
(a) What do you understand by the pH value of a solution?
(b) What is the pH value of water?
(c) Will a given solution be acidic or alkaline if
(i) its pH value is less than 7
(ii) more than 7?
Answer:
(a) In chemistry, pH (/piːˈeɪtʃ/, denoting ‘potential of hydrogen’ or ‘power of hydrogen’) is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions (solutions with higher concentrations of H+ ions) are measured to have lower pH values than basic or alkaline solutions
(b)  the pH value of water is 7
(c)  solution be …………….. if
(i) its pH value is less than 7 then acidic
(ii) more than 7 then basic
Question 9. Concentration of H* (aq) ions in a solution is 10¯¹¹ moles/litre. Calculate its pH value. State the action of
(i) methyl orange,
(ii) phenolphthalein on this solution.
Answer:

Step by Step Explanation:pH = – log([H+])

[H+] = 10^-11 M

pH = – log(10^-11)

pH = – (-11).log(10)

pH = – (-11).1 = 11 [since , log10=1]

Because pH = 11 (7 ≤ pH ≤ 14) the solution is basic in nature

 (i) methyl orange,  yellow
(ii) phenolphthalein on this solution.    pink
Question 10.  Why are common indicators not used to determine the pH value of a solution?
Answer:
 Common indicators doesn’t give specific color in specific solution. Because of this it can’t be used as to find pH value of a solution. They only can determine the nature of the Solution that either the solution is acidic , basic or neutral
Question 11.
(a) What is a universal indicator?
(b) What is the colour of the universal indicator when the pH value is (i) 1 (ii) 5 (iii) 9 (iv) 13 (v) 3 (vi) 7 (vii) 11?
Answer:

 (a)  a universal indicator is a substance that changes to different colours according to whether another substance that touches it is an acid or an alkali

(b) What is the colour of the universal indicator when the pH value is
 (i) 1  red
(ii) 5  yellow
(iii) 9 blue
(iv) 13 violet
 (v) 3  orange
 (vi) 7 green
(vii) 11 indigo
Question 12.

What is the importance of pH value to

(i) a doctor—-
(ii) a food processor
(iii) a cosmetics manufacturer
(iv) a farmer?
Answer
 the importance of pH value to
(i) a doctor-— pH value is a critical factor in the wound healing process and could offer important physiological condition information regarding skin status and infection. It assists physicians with clinically relevant diagnosis and patient wounds care
(ii) a food processor-—Some food processors will need to check pH when making certain food products. Meters that measure pH level are used to insure that food products have an adequate acidity level that will prevent growth of foodborne pathogens
(iii) a cosmetics manufacturer—-In development of a finished product, the pH is carefully considered in order to provide optimal conditions for certain ingredients. In cosmetics, some preservatives and active ingredients may only work or be active at a given pH. For example, enzymes work at a more alkaline pH.
(iv) a farmer–-It is a measure of the acidity or alkalinity of a soil. The study of soil pH is very important in agriculture due to the fact that soil pH regulates plant nutrient availability by controlling the chemical forms of the different nutrients and also influences their chemical reactions

Exercise 2

 Goyal Brothers Class-10 Acid Base and Salts ICSE Chemistry Solutions Ch-3

Page-59

Question 1.

(a) How is the process of titration carried out?
(b) Define the following terms, giving at least two examples.
(i) normal salt, (ii) acid salt, (ii) basic salt

Answer:

(a )Titration, process of chemical analysis in which the quantity of some constituent of a sample is determined by adding to the measured sample an exactly known quantity of another substance with which the desired constituent reacts in a definite, known proportion. The process is usually carried out by gradually adding a standard solution (i.e., a solution of known concentration) of titrating reagent, or titrant, from a burette, essentially a long, graduated measuring tube with a stopcock and a delivery tube at its lower end. The addition is stopped when the equivalence point is reached.

(b)
(i) Normal Salt: A normal salt is a salt formed by the complete replacement of replaceable hydrogen atoms from an acid molecule by means of a metal or a group of elements acting like a metal. Examples: The compounds like KCl, NaCl, FeS04, Na2S04, FeCl2 etc are normal salt

(ii) Acid salts are a class of salts that produce an acidic solution after being dissolved in a solvent. Its formation as a substance has a greater electrical conductivity than that of the pure solvent. An acidic solution formed by acid salt is made during partial neutralization of diprotic or polyprotic acids.

(ii) Alkali salts or basic salts are salts that are the product of incomplete neutralization of a strong base and a weak acid. Rather than being neutral (as some other salts), alkali salts are bases as their name suggests

Question 2.

Pick out (i) soluble salts (ii) insoluble salts from the following list:

(i) ammonium carbonate, (ii) lead sulphate, (iii) copper nitrate, (iv) zinc sulphide, (v) calcium bicarbonate, (vi) sodium sulphite, (vii) aluminium sulphate,
(viii) silver nitrate,  (ix) magnesium bi sulphate, (x) potassium chloride,

Answer:

(i) soluble salts —ammonium carbonate,  sodium sulphite, potassium chloride potassium chloride,magnesium bi sulphate ,silver nitrate,

(ii) insoluble salts —calcium bicarbonate, lead sulphate

Question 3.  Starting from potassium hydroxide and nitric acid, how will you prepare crystals of potassium nitrate?

Answer:

This is a neutralisation reaction of an acid and a base. A reaction between an acid and a base will generally produce a salt and water.

Question 4.  Briefly describe how will you obtain crystals of zinc sulphate starting from zinc and dilute sulphuric acid.

Answer:

To prepare crystals of Zinc sulphate from Zinc and dil. Sulphuric acid. … Divide the filtrate into two parts -evaporate one to dryness to obtain Zinc sulphate in amorphous form and keep the other half of filtrate undisturbed and covered for a day when the crystals of Zinc sulphate will be formed

Question 5.  You are provided with copper carbonate and concentrated sulphuric acid. How will you prepare crystals of hydrated copper
sulphate from the given substances?

Answer:

Copper does not react with dilute sulphuric acid as its reduction potential is higher than that of hydrogen. Copper does not displace hydrogen from non-oxidising acids like HCl or dilute H2SO4.

But, concentrated sulphuric acid is an oxidising agent. So, when copper is heated with conc.H2SO4, a redox reaction occurs and the acid gets reduced to sulphur dioxide.

Cu + 2H2SO4 = CuSO4 + SO2 + 2H2O

The other products of the reaction are copper(II) sulphate and water

Question 6.  You are required to prepare lead sulphate from lead carbonate. Briefly explain how you will proceed.

Answer:

The first step that is required to prepare lead sulphate from lead carbonate is to convert lead carbonate to lead nitrate by reacting it with dilute nitric acid.

PbCO3 + 2HNO3 = Pb(NO3)2 + H2O + CO2

Question 7. Starting from lead nitrate, how will you prepare lead carbonate? Give details of the method you follow

Answer:

The first step that is required to prepare lead sulphate from lead carbonate is to convert lead carbonate to lead nitrate by reacting it with dilute nitric acid

Question 8. We cannot prepare calcium sulphate by treating marble chips with dilute sulphuric acid. Why? Outline the procedure to  prepare calcium sulphate from marble chips

Answer:

when we react them , the calcite present in marble reacts with acid and get corroded and desired result is not formed

Question 9.  Starting from iron and chlorine, describe how will you prepare anhydrous ferric chloride crystals.

Answer:

Ferric chloride FeCl3 is conventionally prepared in an anhydrous form by allowing a chlorine gas to affect glowing iron. As a solution it is in turn obtained by dissolving an iron oxide or carbonate or a metallic iron in a hydrochloric acid or nitrohydrochloric acid.

Question 10.  How can you prepare MgSO47H2O starting from magnesium nitrate crystals?

Answer:

by Titration of magnesium hydroxide  solution with dilute sulphuric acid  (neutralisation)

Mg(OH)2 + H2SO4     —-    MgSO4+ 7 H2O

Question 11.  State three general characteristics of salts.

Answer:

the characteristic properties of salts are:

  • Melting and boiling points: Salts are mostly solids which melt as well as boil at high temperatures.
  • Solubility in water: Salts are generally soluble in water. …
  • Water of crystallization: Generally, salts are found as crystals with water molecules present in them

Question 12.

(a) What do you understand by the term hydrolysis”?

(b) Name two salts which

(i) hydrolyse in water,

(ii) do not hydrolyse in water

Answer:

(a) Hydrolysis- Greek hydro- ‘water’, and lysis ‘to unbind’) is any chemical reaction in which a molecule of water ruptures one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.

(b) Name two salts which

(i) hydrolyse in water,

  • Nacl.
  • KCI.

(ii) do not hydrolyse in water—The salt of strong acid and strong base does not undergo hydrolysis. So sodium sulphate will not undergo hydrolysis in water

Question 13. By writing ionic equations explain why

(i) sodium carbonate solution is alkaline in character?

(ii) ammonium chloride solution is acidic in character?

(iii) potassium chloride solution is neutral in character?

Answer:

(i )Sodium carbonate when dissolved in water is hydrolysed to form a weak acid, carbonic acid and a strong base sodium hydroxide. Hence, an aqueous solution of sodium carbonate is alkaline in nature

(ii)  Ammonium chloride is a salt of a strong acid (HCl) and a weak base (NH3). .The presence of such additional hydrogen ions that are formed due to hydrolysis is responsible for the distinct acidic nature of an aqueous solution of a salt of a strong acid and a weak base like ammonium chloride

(iii) Potassium chloride is a salt of strong acid (HCl) and strong base (KOH). When it is dissolved in water,it shows following reaction. As solution contains equal number of H+ and OH- ions,aqueous solution of potassium chloride is neutral in nature.

Question 14.  While preparing the solution of silver nitrate in distilled water, we always add a few drops of nitric acid. Explain your answer.

Answer:

While preparing the solution of silver nitrate in distilled water, we always add a few drops of nitric acid. because Moreover, silver nitrate easily decomposed in the presence of sunlight, therefore small amount of nitric acid prevent the decomposition of silver nitrate for some time

Question 15.  By giving two examples, define or explain the following terms:
(i) anhydrous salt,  (ii) hydrated salt, (iii) water of crystallisation,
(iv) deliquescent substance, (v) hygroscopic substance, (vi) efflorescent substance.

Answer:

(i) anhydrous salt, ——–anhydrous means without water. anhydrous salt is only the cation and anion making up the salt. All of these hydrated salts can have the water removed by heating and the physical appearance of the dehydrate or anhydrous form of the salt can be quite different from that of the hydrated salt

 (ii) hydrated salt, —A hydrated salt is a crystalline salt molecule that is loosely attached to a certain number of water molecules. Salt is created when an acid’s anion and a base’s cation are combined to produce an acid-base molecule

(iii) water of crystallisation,—–Water of crystallisation is water that is chemically bonded into a crystal structure. Here is the formula for hydrated copper(II) sulfate. … an anhydrous substance contains no water of crystallisation. the degree of hydration is the number of moles of water of crystallisation chemically bonded in 1 mole of the compound

(iv) deliquescent substance, -A deliquescent substance is a material that readily absorbs water out of the air. Deliquescent substances keep absorbing water until they dissolve themselves into liquid solutions. This process is called deliquescence.

(v) hygroscopic substance, —A hygroscopic substance is one that readily attracts water from its surroundings, through either absorption or adsorption. Examples include honey, glycerin, ethanol, methanol, concentrated sulfuric acid, and concentrated sodium hydroxide 

(vi) efflorescent substance.—An efflorescent substance is a chemical which has water associated with its molecules, and which, when exposed to air, loses this water through evaporation. A common example of this phenomenon is the drying of cement

 Objective Type Questions

 I. Multiple Choice Questions

page-59

Choose the correct answer from the options given below :

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II Fill in the Blanks 

Fill in the Blanks space with the choice given in brackets:

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III Choose the Following List

Choose the Following List, as what matches the Description given blew:

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–: end of Acid Base and Salts Solutions Goyal Brothers :–

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