Sulphuric Acid Solutions for ICSE Class 10 Chemistry - Selina

Access ICSE Selina Solutions for Chemistry Class 10 Chapter 11 – Sulphuric Acid (Examples, Easy Methods and Step by Step Solutions) Intext Questions 1. Comment, sulphuric acid is referred to as: a) King of chemicals Ans: Sulphuric acid is known as the King of Che...

Access ICSE Selina Solutions for Chemistry Class 10 Chapter 11 – Sulphuric Acid (Examples, Easy Methods and Step by Step Solutions) Intext Questions 1. Comment, sulphuric acid is referred to as: a) King of chemicals Ans: Sulphuric acid is known as the King of Chemicals because there is no other compound being manufactured and used by such a large number of key industries. (b) Oil of Vitriol Ans: Sulphuric acid is referred to as Oil of vitriol as it was obtained as an oily viscous product of heating crystals of green vitriol. 2. Sulphuric acid is manufactured by contact process. a) Give two balanced equations to obtain SO2 in this process. Ans: Two balanced equations to obtain SO2 is: ( i ) 4 FeS2 + 11O2 → Fe2O3 + 8SO2 ( ii ) S + O2 → SO2 b) Give the conditions for the oxidation of SO2. Ans: The conditions for the oxidation of SO2 are: (i) The temperature should be very low. The yield has been found to be maximum at about 410 ⁰C – 450 ⁰C (ii) High pressure (2 atm) is favourable as the product formed has less volume than reactant. (iii) Excess of oxygen more is the production of sulphur trioxide. c) Name the catalyst used. Ans: Catalysts used are Vanadium pentoxide or platinized asbestos. Class X Chemistry www.vedantu.com 1 d) Why H2SO4 is not obtained by directly reacting SO3 with water? Ans: Sulphuric acid is not obtained directly by reacting SO3 with water because the reaction is highly exothermic and produces the fine misty droplets of sulphuric acid which is directly not absorbed by water. e) Name the chemical used to dissolve SO3 and also name the product formed. Give all the main reactions of this process. Ans: The chemical used to dissolve SO3 is concentrated sulphuric acid and the product formed is oleum. Main reactions of this process are: S + O2 → SO2 V2O5  2 SO2 + O2 ← → 2 SO3 o  450 C SO3 + H 2 SO4 → H 2 S 2O7 H 2 S 2O7 + H 2O → 2 H 2 SO4 f) Name a gas that can be oxidised to sulphur. Ans: H2S (Hydrogen sulphide gas) can be oxidised to sulphur. 3) Why the impurity of arsenic oxide must be removed before passing the mixture of SO2 and air through the catalytic chamber? Ans: Impurity of arsenic oxide must be removed before passing the mixture of SO2 air through the catalytic chamber because it poisons the catalyst (it deactivates the catalyst). 4) Class X Chemistry www.vedantu.com 2 a) Name the catalyst which helps in the conversion of sulphur dioxide to sulphur trioxide in step C. Ans: Vanadium pentoxide or platinized asbestos are the catalyst that helps in the conversion of sulphur to sulphur trioxide in step C. b) In the Contact process for the manufacture of sulphuric acid, sulphur trioxide is not converted to sulphuric acid by reacting it with water. Instead a two steps procedure is used. Write the equations for the two steps involved in D. Ans: The two steps involved in D are: SO3 + H 2 SO4 → H 2 S 2O7 H 2 S 2O7 + H 2O → 2 H 2 SO4 c) What type of substance will liberate sulphur dioxide from sodium sulphite in step E? Ans: Dilute Sulphuric acid will help in the liberation of sulphur dioxide from sodium sulphite in step E. d) Write the equation for the reaction by which sulphur dioxide is converted to sodium sulphite in step F. Ans: Sulphur dioxide is converted to sodium sulphite in step E by the following reaction: 2N 2OH + SO2 → Na2 SO3 + H 2O Exercise Questions: 1) Why is water not added to concentrate H2SO4 in order to dilute it? Ans: Water is not added to concentrated Sulphuric acid since it is an exothermic reaction due to the addition of water to the acid, there is a sudden increase in temperature and the acid being in more amounts tends to spurt which can lead to serious consequences. 2) Give two balanced reactions of each type to show the following properties of sulphuric acid: a) Acidic nature Class X Chemistry www.vedantu.com 3 Ans: (i) Dilute H2SO4 reacts with basic oxides to form sulphate and water. 2 NaOH + H 2 SO4 → Na2 SO4 + 2 H 2O (ii) Sulphuric acid reacts with carbonate to produce Carbon dioxide (CO2). Na2CO3 + H 2 SO4 → Na2 SO4 + H 2O + CO2 ↑ b) Oxidising agent Ans: H 2 SO4 → H 2O + SO2 + [O ] Nascent oxygen oxidizes non-metals, metals and inorganic compounds. For example, Carbon to carbon dioxide C + H 2 SO4 → CO2 + H 2O + 2 SO2 c) Dehydrating Nature: Ans: It has great affinity for water. It readily absorbs moisture from atmospheric air. Conc. H 2 SO4 HCOOH → CO + H 2O Conc. H 2 SO4 C6 H12O6 → 6C + 6 H 2O d) Non-volatile nature: Ans: It has a high boiling point that is why it is considered to be non-volatile. Therefore, it is used in the preparation of volatile acids like hydrochloric acid, nitric acid from their salts by double decomposition reaction. NaCl + H 2 SO4 → NaHSO4 + HCl KCl + H 2 SO4 → KHSO4 + HCl 3) Give a chemical test to distinguish between: a) Dilute sulphuric acid and dilute hydrochloric acid (using lead nitrate solution). Ans: Bring a glass rod dipped in Ammonia solution near the mouth of each test tube containing dil. HCl and dil. H2SO4 each. Dilute HCl Dil. H2SO4 Class X Chemistry www.vedantu.com 4  White fumes of ammonium chloride No such fumes are produced. are formed. b) Dilute sulphuric acid and concentrated sulphuric acid. Ans: 1. Dilute sulphuric acid treated with zinc gives Hydrogen gas with a pop sound. Concentrated H2SO4 gives SO2 gas with zinc and the gas turns Acidified potassium dichromate paper into green color. 4) Write balanced chemical equations: when hot and concentrated sulphuric acid reacts with the following: a) Sulphur Ans: On reaction of sulphuric acid with sulphur the product formed is Sulphur dioxide is formed. S + 2 H 2 SO4 3SO2 + 2 H 2O (b) NaOH Ans: On reaction of sulphuric acid with sodium hydroxide it neutralizes base to form sodium sulphate. 2 NaOH + H 2 SO4 → Na2 SO4 + 2 H 2O (c) Sugar Ans: On reaction of sulphuric acid with sugar it forms carbon. Conc. H 2 SO4 C12 H 22O11 → 12C + 11H 2O (d) Carbon Ans: On reaction of sulphuric acid with carbon it forms carbon dioxide and sulphur dioxide gas. C + 2 H 2 SO4 → CO2 + 2 H 2O + 2 SO2 ↑ (e) Copper Ans: On reaction of sulphuric acid with copper it forms copper sulphate and sulphur dioxide. Cu + H 2 SO4 → CuSO4 + 2 H 2O + SO2 ↑ Class X Chemistry www.vedantu.com 5 5) Why is: a) Concentrated sulphuric acid kept in air- tight bottles? Ans: Concentrated sulphuric acid is a hygroscopic substance that absorbs moisture when exposed to air. Therefore it is stored in air -tight bottles. b) H2SO4 is not used as a drying agent for H2S? Ans: Sulphuric acid is not a drying agent for H2S because it reacts with H2S to form sulphur. H 2 SO4 + H 2 S → 2 H 2O + SO2 + S ↓ (c) Sulphuric acid used in the preparation of HCl and HNO3? Give equations in both cases. Ans: Concentrated sulphuric acid has high boiling point (356 oC). So, it is considered to be non-volatile. Therefore it is used in the preparation of volatile acids like Hydrochloric acid and Nitric acids from their salts by double decomposition. NaCl + H 2 SO4 → NaHSO4 + HCl NaNO3 + H 2 SO4 → NaHSO4 + HNO3 6) What property of conc. H2SO4 is made use of in each of the following cases? Give an equation for the reaction in each case: a) In the production of HCl gas when it reacts with a chloride, Ans: On heating with NaCl conc. Sulphuric acid evolves pungent fumes of HCl gas. Property: Reducing property. Δ NaCl + H 2SO 4  → NaHSO 4 + HCl (Conc.) Sodium Sodium Sulphuric Hydrogen Hydrogen chloride acid sulphate Chloride b) In the preparation of CO from HCOOH. Ans: Property: Dehydrating agent. Class X Chemistry www.vedantu.com 6  Conc.H 2SO4 HCOOH → CO + H 2O Formic acid Carbon Water − monooxide c) As a source of hydrogen by diluting it and adding a strip of magnesium. Ans: Acidic property: According to the reactivity series, magnesium is present above hydrogen therefore sulphuric acid releases hydrogen gas upon reacting with magnesium strips. Mg + H 2SO4 → MgSO4 + H 2 d) In the preparation of sulphur dioxide by warming a mixture of conc. Sulphuric acid and copper-turnings. Ans: Oxidizing property – This property of concentrated H2SO4 is due to thermal decomposition. Cu + H 2 SO4 → CuCO4 + 2 H 2O + SO2 e) Hydrogen sulphides gas is passed through concentrated sulphuric acid. Ans: When hydrogen sulphide is passed through concentrated sulphuric acid, it releases sulphur dioxide to form sulphur. H 2S + H 2SO4 → S + 2H 2 O + SO 2 f) Its reaction with (i) ethanol (ii) carbon. Ans: i) Reaction with Ethanol. C + 2H 2SO4 → CO 2 + 2H 2 O + 2SO 2 ↑ ii) Reaction with carbon. Conc. H 2SO4 C2 H 5OH  1700 C → C2 H 4 ↑ + H 2O Ethylene 7) What is the name given to the salts of: a) Sulphurous acid Ans: The name of the salt is hydrogen sulphite and Sulphite. b) Sulphuric acid Class X Chemistry www.vedantu.com 7 Ans: The name of the salt is Sulphate and Bisulphate. 8) Give reasons for the following. (a) Sulphuric acid forms two types of salts with NaOH. Ans: When Sulphuric acid reacts with NaOH it forms two types of salts as it is dibasic in nature. NaOH+H 2SO 4 → NaHSO 4 +H 2O 2NaOH+H 2SO 4 → Na 2SO 4 +2H 2O (b) A piece of wood becomes black when concentrated sulphuric acid is poured on it. Ans: When Conc. Sulphuric acid is poured on a piece of wood huge mass of carbon is produced causing it to turn black. (c) Brisk effervescence is seen when oil of vitriol is added to sodium carbonate. Ans: When oil vitriol is added to sodium carbonate brisk effervescence are seen due to the evolution of Carbon dioxide. Na 2 CO3 +H 2SO 4 → Na 2SO 4 +H 2 O+CO ↑ 9. Copy and complete the following table: Column 1 Column 2 Column 3 Substance reacted Dilute or Gas with acid concentrated acid Hydrogen Carbon dioxide Only chlorine Ans: Column 1 Column 2 Column 3 Substance reacted Dilute or Gas with acid concentrated acid Zinc Dilute sulphuric acid Hydrogen Class X Chemistry www.vedantu.com 8  Concentrated sulphuric Calcium carbonate Carbon dioxide acid Bleaching powder Dilute sulphuric acid Only chlorine CaOCl2 10) Following are the typical properties of dilute acid. Complete them by inserting suitable words: i) Active metal+ acid Ans: Active metal → Salt + Hydrogen gas ii) Base+ Acid Ans: Base + Acid → Salt + water iii) Carbonate/ hydrogen carbonate + Acid Ans: Hydrogen carbonate / carbonate + Acid → Salt + Water + Carbon dioxide iv) Sulphite/hydrogen sulphite + Acid Ans: Sulphite / Hydrogen sulphite + Acid → Salt + Water + Sulphur dioxide v) Sulphide + Acid Ans: Sulphide + Acid → Salt + Hydrogen Sulphide 11) a) Which property of sulphuric acid accounts for its use as a dehydrating agent? Ans: Sulphuric acid is powerful dehydrating agent on account of its strong affinity towards water. b) Concentrated sulphuric acid is both an oxidizing agent and a non-volatile acid. Write one equation. Each to illustrate the above mentioned properties of sulphuric acid. Ans: Concentrated sulphuric acid as i. Oxidising agent: The oxidising property of conc. sulphuric acid its due to the fact that on thermal decomposition, it gives nascent oxygen [O]. H 2O + SO2 + [O ] H 2 SO4 →     Class X Chemistry www.vedantu.com 9 ii. Non-volatile acid: Conc. sulphuric acid has high boiling point which is why it is said to be a non - volatile compound. Hence it is used for preparing volatile acids like hydrochloric acids, nitric acids from their salts by the process of double decomposition. H 2 SO4        + NaCl → NaHSO4 + HCl 12) Some properties of sulphuric acid are listed below. Choose the property A, B, C or D which is responsible for the reactions (i) to (v). Some properties may be repeated: A. Acid B. Dehydrating agent C. Non-volatile acid D. Oxidising agent ( i ) C12 H 22O11 + nH 2 SO4 12C + 11H 2O + nH 2 SO4 ( ii ) S + 2 H 2 SO   4 3SO2 +2 H 2O ( iii ) NaCl + H 2 SO4 NaHSO4 + HCl ( iv ) CuO + H 2 SO4     CuSO4 + H 2O ( v ) Na2CO3 + H 2 SO4 Na2 SO4 + H 2O + CO2 Ans: (i) C12H22O11 + nH2SO4 → 12C + 11H2O + nH2SO4 - Dehydrating agent (ii) S + 2H2SO4 → 3SO2 +2H2O – Oxidising agent (iii) NaCl + H2SO4 → NaHSO4 + HCl – Non – volatile agent (iv) CuO + H2SO4 → CuSO4 +H2O – Acid (v) Na2CO3 + H2SO4 → Na2SO4 + H2O +CO2 – Acid 13) a) Name the acid formed when sulphur dioxide dissolves in water. Ans: Sulphurous acid is formed when sulphur dioxide dissolves in water. Class X Chemistry www.vedantu.com 10 (b) Name the gas released when sodium carbonate is added to a solution of sulphur dioxide. Ans: Carbon dioxide gas is released when sodium carbonate is added to the solution of sulphur dioxide. 2008 a) Dilute sulphuric acid will produce a white precipitate when added to a solution of: i. Copper nitrate ii. Zinc nitrate iii. Lead nitrate iv. Sodium nitrate Ans: Dilute sulphuric acid will produce a white precipitate when added to a solution of Lead nitrate. b) Identify the following substance: Liquid E can be dehydrated to produce ethene. Ans: Liquid E is ethanol. It can be dehydrated to produce ethene. c) Copy and complete the following table relating to an important industrial process and its final output. Equation for Name of Inputs Catalyst catalyzed reaction process output Contact Sulphur dioxide + process oxygen Ans: Equation for Name of Inputs Catalyst catalyzed reaction Output process output Contact Sulphur dioxi Sulphuric Platinum or V2O5 2SO2 + O2 ⇄ 2SO3 process de + oxygen acid Class X Chemistry www.vedantu.com 11 d) Making use only of substances given: dil. sulphuric acid, sodium carbonate, zinc, sodium, sulphite, and lead, calcium carbonate: Give equations for the reactions by which you could obtain: i. hydrogen ii. sulphur dioxide iii. carbon dioxide iv. zinc carbonate [2 steps] Ans: i) Zn + dil. H2SO4 → ZnSO4 + H2 ii. Na2CO3 + dil. H2SO4 → Na2SO4 + H2O + CO2 iii. Pb(NO3) + dil. H2SO4 → PbSO4 + 2HNO3 iv. Zn + dil. H2SO4 → ZnSO4 + H2 v. ZnSO4 + Na2CO3 → ZnCO3 + Na2SO4 e) What property of conc. H2SO4: i. Is used in the action when sugar turns black in its presence. Ans: The Dehydrating property of concentrated sulphuric acid allows it to be used in the action where sugar turns black in its presence. ii. Allows it to be used in the preparation of HCl and HNO3 acids. Ans: The non - volatile property of concentrated sulphuric acid allows it to be used in the preparation of hydrogen chloride and nitric acid. f) Write the equations for: i. dil. H2SO4 and barium chloride. Ans: H2SO4 + BaCl2 → BaSO4 + 2HCl ii. dil. H2SO4 and sodium sulphide. Ans: Na2 S + H 2 SO4 → Na2 SO4 + H 2 S 2009 a) Name the gas evolved [formula is not acceptable]. The gas that can be oxidised to sulphur. Class X Chemistry www.vedantu.com 12 Ans: Hydrogen Chloride 2010 a. Give the equation for: i. Heat on sulphur with conc. sulphuric acid Ans: S + H 2 SO4 → 3SO2 + 2 H 2O ii. Reaction of - sugar with conc. sulphuric acid. Ans: C12 H 22O11 + Conc.H 2 SO4 → 6C + 6 H 2O b. Give a balanced equation for the conversion of zinc oxide to zinc sulphate. Ans: Zn + H 2 SO4 → ZnSO4 + H 2O c. Select the correct answer from A, B, C. A. Sodium hydroxide solution B. A weak acid C. Dilute sulphuric acid. The solution which liberates sulphur dioxide gas, from sodium sulphite. Ans: Option (C) is the correct answer. Dilute sulphuric acid liberates sulphur dioxide gas from sodium sulphite. 2011 a) State your observation when - Sugar crystals are added to a hard glass test tube containing conc. sulphuric acid. Ans: When Sugar crystals are added to a hard glass test tube containing conc. sulphuric acid charring of sugar takes place. Sulphuric acid dehydrates sugar leaving behind carbon which is black in colour. b. Choose the correct answer from the choices - The gas evolved when dil. sulphuric acid reacts with iron sulphide. i. Hydrogen sulphide ii. Sulphur dioxide iii. Sulphur trioxide iv. Vapour of sulphuric acid Class X Chemistry www.vedantu.com 13 Ans: Option (i) is the correct answer. Hydrogen sulphide gas is evolved when dil. sulphuric acid reacts with iron sulphide. c. Give a balanced equation for: i. Dilute sulphuric acid is poured over sodium sulphite. Ans: Na 2S+dil.H 2SO 4 → Na 2SO 4 + H 2S ii. Manufacture of sulphuric acid by the - contact process. Ans: Formation of Sulphur dioxide: S+O2 → SO2 Conversion of SO2 to SO3: V2O 3 /Pt  2SO 2 + O 2 ← → 2SO3 0  400−450 C Conversion of sulphur trioxide to oleum: SO 3 + H 2SO4 → H 2S2 O7 Dilution of Oleum: H 2S2 O7 + H 2 O → 2H 2SO 4 d. State the property of sulphuric acid shown by the reaction of conc. sulphuric acid when heated with i. Potassium nitrate Ans: conc. sulphuric acid when heated with Potassium nitrate – property shown is Non-volatile nature. ii. Carbons Ans: conc. sulphuric acid when heated with Carbon – property shown is an oxidising agent. iii. Ethanol Ans: Concentrated sulphuric acid when heated with ethanol yields ethene. Therefore it shows its dehydrating property. Class X Chemistry www.vedantu.com 14 2012 a) Name - The gas produced on reaction of dilute sulphuric acid with a metallic sulphide. Ans: Hydrogen Sulphide (H2S) gas is produced in reaction of dilute sulphuric acid with a metallic sulphide. b. Some properties of sulphuric acid are listed below. Choose the role played by sulphuric acid as A, B, C or D which is responsible for the reactions (i) to (v). Some roles may be repeated. A) Dilute acid B) Dehydrating agent C) Non-volatile acid D) Oxidising agent Conc. H 2SO4 i. CuSO 4.5H 2O  → CuSO 4 +5H 2O Ans: Dehydrating agent ii. S + 2H 2SO 4 [conc.] → 3SO 2 + 2H 2O Ans: Oxidising agent iii. NaNO 2 +H 2SO 4  → NaHSO 4 +HNO 3 [Conc.] 0