{"id":16268,"date":"2017-07-18T06:02:51","date_gmt":"2017-07-18T06:02:51","guid":{"rendered":"https:\/\/www.aplustopper.com\/?p=16268"},"modified":"2020-11-25T18:05:21","modified_gmt":"2020-11-25T12:35:21","slug":"selina-icse-solutions-class-10-chemistry-electrolysis","status":"publish","type":"post","link":"https:\/\/www.aplustopper.com\/selina-icse-solutions-class-10-chemistry-electrolysis\/","title":{"rendered":"Selina Concise Chemistry Class 10 ICSE Solutions Electrolysis"},"content":{"rendered":"

Selina Concise Chemistry Class 10 ICSE Solutions Electrolysis<\/span><\/h2>\n

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 10 Chemistry Chapter 6 Electrolysis. You can download the Selina Concise Chemistry ICSE Solutions for Class 10 with Free PDF download option. Selina Publishers Concise Chemistry for Class 10 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.<\/p>\n

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ICSE Solutions<\/a>Selina ICSE Solutions<\/a><\/p>\n

Selina ICSE Solutions for Class 10 Chemistry Chapter 6 Electrolysis<\/strong><\/p>\n

Exercise Intext 1<\/strong><\/span><\/p>\n

Solution 1.<\/strong><\/span><\/p>\n

(a) Powdered sodium chloride (common salt) does not conduct an electric current<\/a>, but it does so when\u00a0dissolved in water<\/u>\u00a0or when\u00a0melted<\/u>.<\/p>\n

(b) Molten lead bromide conducts electricity .It is called an\u00a0electrolyte<\/u>. It is composed of lead\u00a0ions<\/u>\u00a0and bromide\u00a0ions<\/u>. The lead ions are\u00a0positively<\/u>charged and are called\u00a0cations<\/u>. The bromide\u00a0ions<\/u>\u00a0are\u00a0negatively<\/u>\u00a0charged and are called\u00a0anions<\/u>.<\/p>\n

(c) Substances which conduct electricity<\/a> in the solid state are generally\u00a0metals.<\/u><\/p>\n

(d) The electron releasing tendency of zinc is\u00a0more<\/u>\u00a0than that of copper.<\/p>\n

(e) A solution of\u00a0HCl\u00a0gas in water conducts electricity because\u00a0it\u00a0ionizes,<\/u>\u00a0but a solution of\u00a0HCl\u00a0gas in toluene does not conduct an electric current because\u00a0it does not ionize in toluene.<\/u><\/p>\n

Solution 2.<\/strong><\/span><\/p>\n

(a) Electrolysis<\/a>: It is the process of decomposition of a chemical compound in aqueous solutions or in molten state accompanied by a chemical change using direct electric current.<\/p>\n

(b) Non-electrolyte: It is a compound which neither in solution nor in the molten state allows an electric current to pass through it.<\/p>\n

(c)\u00a0Cation\u00a0and anion<\/a>: Atoms which carry positive charge are called\u00a0cations.
\nAtoms which carry negative charge are called anions.<\/p>\n

(d) Weak electrolyte: Electrolytes which allow small amount of electricity to flow through them and are partially dissociated in fused or aqueous solution are called weak electrolyte.<\/p>\n

Solution 3.<\/strong><\/span><\/p>\n

(a) Difference between Modern explanation and Arrhenius explanation for the theory of electrolysis:
\nArrhenius considered that water ionizes electrolytes but Modern theory explained that electrolytes are ionic even in solid state and their ions are held by strong electrostatic forces which make them immobile. Water renders these ions mobility by breaking the electrostatic forces.<\/p>\n

(b) Difference between electrolytic dissociation and ionization :<\/p>\n\n\n\n\n\n
Ionisation<\/strong><\/td>\nDissociation<\/strong><\/td>\n<\/tr>\n
1. Formation of positively or negatively charged ions from molecules which are not initially in the ionic state.<\/td>\n1. Separation of ions which are already present in an ionic compound.<\/td>\n<\/tr>\n
2. Polar covalent compounds show ionization. e.g.\u00a0HCl, H2<\/sub>CO3<\/sub>, NH4<\/sub>OH etc.<\/td>\n1. Electrovalent compounds show dissociation. e.g. Potassium chloride , lead bromide, etc.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(c) A\u00a0cation\u00a0and anion:<\/p>\n\n\n\n\n\n\n
Cation<\/strong><\/td>\nAnion<\/strong><\/td>\n<\/tr>\n
1. Are positively charged ions.<\/td>\nAre negatively charged ions.<\/td>\n<\/tr>\n
2. Migrate to cathode during electrolysis.<\/td>\nMigrate to anode during electrolysis.<\/td>\n<\/tr>\n
3. Gain electron from the cathode and get reduced to become a neutral atom.<\/td>\nLose electrons to the anode and get oxidized to become a neutral atom.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(d) Electrolytic dissociation and thermal dissociation:
\nElectrolytic dissociation is the dissociation of an electrovalent compound<\/a> into ions in the fused state or in aqueous solution state.<\/p>\n

Thermal dissociation: Reversible breakdown of a chemical compound into simpler substances by heating it. The splitting of ammonium chloride into ammonia and hydrogen chloride is an example. On cooling, they recombine to form the salt.<\/p>\n

Solution 4.<\/strong><\/span><\/p>\n

(a) Sodium carbonate
\n(b) NH4<\/sub>OH
\n(c) An inert electrode: graphite and Active electrode: silver
\n(d) H+
\n<\/sup>(e) Electrode is cathode
\n(f) Graphite<\/p>\n

Solution 5.<\/strong><\/span><\/p>\n

Electrolysis is a\u00a0redox\u00a0process<\/a>. The reaction at the cathode involves reduction of\u00a0cations\u00a0as they gain of electrons while the reaction at anode involves oxidation of anions as they loss of electrons to become neutral.
\nExample: Dissociation of sodium chloride during electrolysis.
\n\"\"
\n<\/sup>Cathode : Na+<\/sup>\u00a0+ e–<\/sup>\u00a0\u2192 Na (reduction)
\nCl–<\/sup>\u00a0– e–\u00a0<\/sup>\u2192 Cl (oxidation)
\nCl\u00a0+\u00a0Cl\u00a0\u2192 Cl2
\n<\/sub>Overall reaction: 2NaCl\u00a0\u2192 2Na + Cl2<\/sub><\/p>\n

Exercise Intext 2<\/strong><\/span><\/p>\n

Solution 1.<\/strong><\/span><\/p>\n

(a) Glucose, Kerosene
\n(b)\u00a0NaCl\u00a0and\u00a0NaOH
\n(c) CH3<\/sub>COOH\u00a0and NH4<\/sub>OH<\/p>\n

Solution 2.<\/strong><\/span><\/p>\n

(a)\u00a0Cane sugar is a compound which does not have ions even in solution and contains only molecules. Hence, it does not conduct electricity. On the other hand, sodium chloride solution contains free mobile ions and allows electric current to pass through it. This makes it a good conductor of electricity.<\/p>\n

(b)\u00a0Hydrochloric acid is a strong electrolyte and dissociates completely in aqueous solution. The solution contains free mobile ions which allow electric current to pass through it. Hence, hydrochloric acid is a good conductor of electricity.<\/p>\n

(c)\u00a0Hydrogen is placed lower in the electrochemical series and sodium is placed at a higher position. This is because H+<\/sup>\u00a0ions are discharged more easily at the cathode than Na+\u00a0<\/sup>during electrolysis and gains electrons more easily.
\nTherefore, H+<\/sup>\u00a0ion is reduced at the cathode and not Na+<\/sup>\u00a0ion.<\/p>\n

Solution 3.<\/strong><\/span><\/p>\n

(a) Zn occurs readily as ion whereas Cu occurs more readily as metal in nature.<\/p>\n

(b) Copper is above silver in the electrochemical series and is thus more reactive than silver. So, copper displaces silver from silver nitrate. Hence, we cannot store AgNO3<\/sub>\u00a0solution in copper vessel.
\nCu +AgNO3<\/sub>\u00a0\u2192 Cu(NO3<\/sub>)2<\/sub>\u00a0+ 2Ag<\/p>\n

(c) Copper is more active than Ag.<\/p>\n

Solution 4.<\/strong><\/span><\/p>\n

(a) By treating its salt with a more reactive metal.
\n(b) By supplying two electrons to Cu+2
\n<\/sup>Cu+2\u00a0<\/sup>+ 2e–\u00a0<\/sup>\u2192 Cu<\/p>\n

Solution 5.<\/strong><\/span><\/p>\n

In the aqueous state, the slightly negatively charged oxygen\u00a0atoms of the polar water molecule exerts\u00a0a pull on the positively charged sodium ions. A similar pull is exerted by the slightly charged hydrogen atoms of the water on the negatively charged chloride ions. Thus the ions become free in solution. These free ions conduct electricity.
\nIn the molten state, the high temperatures required to melt the solid weakens the bond between the particles and the ions are set free.<\/p>\n

Solution 6.<\/strong><\/span><\/p>\n

(a) Two anions are\u00a0and OH–<\/sup>.<\/p>\n

(b) OH–<\/sup>\u00a0is discharged at anode and the main product of the discharge of OH–<\/sup>\u00a0is O2
\n<\/sub>Reaction is :
\nOH–\u00a0<\/sup>\u2192 OH + e–
\n<\/sup>4OH\u00a0\u2192 2H2<\/sub>O + O2<\/sub><\/p>\n

(c) The product formed at cathode is hydrogen. The reaction is :
\nH+<\/sup>\u00a0+ e–<\/sup>\u00a0\u2192 H
\nH + H\u00a0\u2192 H2
\n<\/sub><\/p>\n

(d) No change in\u00a0colour\u00a0is observed.<\/p>\n

(e) Dilute\u00a0sulphuric\u00a0acid\u00a0catalyse\u00a0the dissociation of water molecules into ions, hence electrolysis of acidified water is considered as an example of catalysis.<\/p>\n

Solution 7.<\/strong><\/span><\/p>\n

(a)\u00a0Labelled<\/span>\u00a0diagram of electrolytic cell is:
\n\"\"
\n(b) The ions present in the cell are Cu2+<\/sup>, H+<\/sup>, SO4<\/sub>2-<\/sup>\u00a0,\u00a0OH–<\/sup>.
\n(c) SO4<\/sub>2-<\/sup>\u00a0and OH–<\/sup>\u00a0ions both migrate towards anode.
\n(d) Both Cu2+<\/sup>\u00a0and H+<\/sup>\u00a0ions migrate towards cathode.
\n(e) SO4<\/sub>2-<\/sup>\u00a0and H+<\/sup>\u00a0will not discharge at electrodes.
\n(f) Reaction at cathode:
\nCu+2<\/sup>\u00a0+2e–<\/sup>\u00a0\u2192 Cu
\n(g) Reaction at anode:
\nOH–<\/sup>\u00a0– e–<\/sup>\u00a0\u2192 OH
\n2OH + 2OH\u00a0\u2192 2H2<\/sub>O + O2
\n<\/sub>(h)\u00a0Sulphate\u00a0ions are the spectator ions because they do not change in the reaction.<\/p>\n

Solution 8.<\/strong><\/span><\/p>\n

(a) Reaction at anode during the electrolysis ofvery dilute\u00a0sulphuric\u00a0acid:
\nOH–<\/sup>\u00a0\u2192 OH + e–
\n<\/sup>4OH\u00a0\u2192 2H2<\/sub>O + O2<\/sub><\/p>\n

(b) Reaction at anode during the electrolysis of aqueous copper\u00a0sulphate\u00a0solution
\n4OH–<\/sup>\u00a0\u2192 4OH + 4e–
\n<\/sup>4OH\u00a0\u2192 2H2<\/sub>O + O2<\/sub><\/p>\n

(c) Reaction at anode during the electrolysis of sodium chloride solution
\n2Cl–<\/sup>\u00a0\u2192 Cl2<\/sub>\u00a0+ 2e–<\/sup><\/p>\n

(d) Reaction at anode during the electrolysis of fused lead bromide
\nBr–<\/sup>\u00a0– e–\u00a0<\/sup>\u2192 Br
\nBr + Br\u00a0\u2192 Br2<\/sub><\/p>\n

(e) Reaction at anode during the electrolysis of magnesium chloride (molten)
\n2Cl–<\/sup>\u00a0\u2192 Cl2<\/sub>\u00a0+2e–
\n<\/sup><\/p>\n

(f) Concentrated HCl,
\nHCl in the pure liquid state is unionised and hence does not conduct electricity.<\/p>\n

(g) Very dilute HCl,
\nCl–<\/sup>\u00a0– e–<\/sup>\u00a0\u2192 Cl
\nCl\u00a0 + Cl\u00a0 \u2192 Cl2<\/sub><\/p>\n

Solution 9.<\/strong><\/span><\/p>\n

(a) Electrolyte
\n(b) Nickel
\n(c) Cathode
\n(d) Anode
\n(e) Cations<\/p>\n

Exercise 1<\/strong><\/span><\/p>\n

Solution 1.<\/strong><\/span><\/p>\n

(a) During electrolysis of lead bromide, there is loss of electrons at anode by bromine and gain of electrons at cathode by lead. Thus oxidation and reduction go side by side. Therefore, it is a\u00a0redox\u00a0reaction.
\nPbBr2<\/sub>\u00a0\u2192 Pb+2<\/sup> + 2Br–<\/sup><\/p>\n

(b) The blue\u00a0colour\u00a0of copper ions fades due to decrease in Cu+2<\/sup>\u00a0ions and finally the solution becomes\u00a0colourless\u00a0as soon as Cu+2<\/sup>\u00a0ions are finished.<\/p>\n

(c) Lead bromide dissociate into ions in the molten state whereas it does not dissociate in solid state. The ions become free when lead bromide is in molten state but in the solid state the ions are not free since they are packed tightly together due to electrostatic force between them. Therefore, lead bromide undergoes electrolytic dissociation in the molten state.<\/p>\n

(d)\u00a0Aluminium\u00a0has great affinity towards oxygen, so it is not reduced by reducing agent. Therefore it is extracted from its oxide by electrolytic reduction.<\/p>\n

(e) As per electrolytic reactions, 4H+1<\/sup>\u00a0are needed at cathode and 4OH–<\/sup>\u00a0at the anode and two molecules of water are produced at the anode. Hence for every two molecules of water, two molecules of hydrogen and one molecule of oxygen are liberated at the cathode and anode respectively.
\n\"\"<\/p>\n

(f) This is because HNO3<\/sub>\u00a0is volatile.<\/p>\n

(g) Ammonia is a covalent compound. Therefore, it is unionized in the gaseous state but in the aqueous solution it gives NH4<\/sub>OH which is a weak electrolyte and dissociates into ions.<\/p>\n

(h) Graphite is unaffected by the bromine\u00a0vapours.<\/p>\n

(i) Silver nitrate is not used as electrolyte for electroplating with silver because the deposition of silver will be very fast and hence not very smooth and uniform.<\/p>\n

(j)\u00a0Carbon tetrachloride is a liquid and does not conduct electricity because it is a covalent compound and there are no free ions present and contain only molecules.<\/p>\n

Solution 2.<\/strong><\/span><\/p>\n

(a) Strong electrolyte : Dilute hydrochloric acid, dilute\u00a0sulphuric\u00a0acid, ammonium chloride, sodium acetate
\n(b) Weak electrolyte: Acetic acid, ammonium hydroxide
\n(c) Non-electrolyte: Carbon tetrachloride<\/p>\n

Solution 3.<\/strong><\/span><\/p>\n

(a) Molecules
\n(b) Will not<\/p>\n

Solution 4.<\/strong><\/span><\/p>\n

Water is a non-conductor of electricity and consists entirely of molecules. It can be\u00a0electrolytically<\/span>\u00a0decomposed by addition of traces of dilutesulphuric<\/span>\u00a0acid which dissociate as H+<\/sup>\u00a0and SO4<\/sub>2-<\/sup>\u00a0ions and help in dissociating water into H+<\/sup>\u00a0and OH–<\/sup>, water being a polar solvent.<\/p>\n

Solution 5.<\/strong><\/span><\/p>\n\n\n\n\n\n
<\/td>\nAnode<\/strong><\/td>\nElectrolyte<\/strong><\/td>\nCathode<\/strong><\/td>\n<\/tr>\n
Silver plating of spoon<\/td>\nPlate of pure clean silver<\/td>\nSolution of potassiumargentocyanide<\/td>\nArticle to be electroplated<\/td>\n<\/tr>\n
Purification of copper<\/td>\nImpure copper<\/td>\nSolution of coppersulphate\u00a0and dilutesulphuric\u00a0acid<\/td>\nThin strip of pure copper<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Solution 6.<\/strong><\/span><\/p>\n

Electricity, Chemical<\/p>\n

Solution 7.<\/strong><\/span><\/p>\n

(b)\u00a0CuSO4<\/sub>\u00a0is preferred as an electrolyte.<\/p>\n

(c)\u00a0The copper anode continuously dissolves as ions in solution and is replaced periodically. The electrolyte dissociates into Cu+2<\/sup>\u00a0ions which migrate towards the iron object taken as the cathode and are deposited as neutral copper atoms on the cathode.
\nElectrolyte<\/b><\/strong>: Aqueous solution of nickel sulphate
\nDissociation<\/b><\/strong>: CuSO4<\/sub>\u00a0\u2192 Cu2+<\/sup>\u00a0+ SO4<\/sub>2-<\/sup>
\nH2<\/sub>O \u2192 H+<\/sup>\u00a0+ OH–
\n<\/sup>Electrodes:
\n<\/b><\/strong>Cathode: Article to be electroplated
\nAnode: Block of pure copper
\nElectrode reactions:<\/b><\/strong>
\nReaction at cathode: Cu2+<\/sup>\u00a0+ 2e–<\/sup>\u2192 Cu (deposited)
\nReaction at anode:\u00a0Cu – 2e–<\/sup>\u2192 Cu2+<\/sup><\/p>\n

Solution 1 (2004).<\/strong><\/span><\/p>\n

(a) X \u2192 X2+<\/sup>\u00a0+ 2e–<\/sup>\u00a0,\u00a0Y + 3e– <\/sup>\u2192 Y3-
\n<\/sup>(b) Y2<\/sub>\u00a0+ 3X\u00a0\u2192 X3<\/sub>Y2
\n<\/sub>(c) (i) It is used for the electroplating of metals.
\n(ii) It is also used in purification of metals.
\n(d) Cathode, Anode<\/p>\n

Solution 1 (2005).<\/strong><\/span><\/p>\n

(a) Because Copper is an electronic conductor as it is a metal.
\n(b) In solid sodium chloride, Na+<\/sup>\u00a0and\u00a0Cl\u00a0–<\/sup>\u00a0ions are not free due to strong electrostatic forces of attraction among them. The\u00a0ions,\u00a0therefore are unable to move to any large extent when electric field is affected. Hence no current.<\/p>\n

Solution 1 (2006).<\/strong><\/span><\/p>\n

(a) (i) The name of electrode A is Platinum anode and that of electrode B is platinum or copper cathode.
\n(ii) Anode\u00a0act\u00a0as oxidizing electrode.
\n(b) AgNO3\u00a0<\/sub>solution will turn blue.<\/p>\n

Solution 1 (2007).<\/strong><\/span><\/p>\n

(i) Molten ionic compound: Strong electrolytes
\n(ii) Carbon tetrachloride: Non-electrolyte
\n(iii) An\u00a0aluminium\u00a0wire: Metallic conductor
\n(iv) A solution containing solvent molecules, solute molecules and ions formed by dissociation of solute molecules: Weak electrolyte
\n(v) A sugar solution with sugar molecules and water molecules: Non- electrolyte<\/p>\n

Solution 1 (2008).<\/strong><\/span><\/p>\n

(a) The reaction takes place at anode. This is an example of oxidation.
\n(b) Cu+2<\/sup>\u00a0will discharge easily at cathode.
\nReaction at cathode:
\nCu+2<\/sup>\u00a0+2e–<\/sup>\u00a0\u2192 Cu
\n(c) Carbon tetrachloride is a non-electrolyte because it is a covalent compound. It does not ionize and hence do not conduct electricity.<\/p>\n

Solution 2 (2004).<\/strong><\/span><\/p>\n

(a) Non-electrolyte contains molecules.
\n(b) Molecules of HX and H+<\/sup>\u00a0and X–<\/sup>\u00a0ions.
\n(c) Loss
\n(d) The electrolyte used for the purpose must contain the ions of metal which is to be electroplated on the article.
\n(e) The reaction at the cathode involves reduction of\u00a0cations\u00a0as they gain electrons to become neutral atoms while that at anode involves oxidation of anions as they lose electrons to become neutral.
\nExample: Dissociation of sodium chloride during electrolysis.
\nNaCl\u00a0\u2192 Na+<\/sup>\u00a0+\u00a0Cl–
\n<\/sup>At cathode: Na+<\/sup>\u00a0+ e–<\/sup>\u00a0Na (Reduction)
\nAt anode:\u00a0Cl–<\/sup>\u00a0– e–<\/sup>\u00a0\u2192 Cl(oxidation)
\nCl\u00a0+\u00a0Cl\u00a0\u2192 Cl2
\n<\/sub>Overall reaction: 2NaCl\u00a0\u2192 2Na + Cl2<\/sub><\/p>\n

Solution 2 (2005).<\/strong><\/span><\/p>\n

Hydrogen gas is released at cathode when acidulated water is electrolyzed.<\/p>\n

Solution 2 (2008).<\/strong><\/span><\/p>\n

During the electrolysis of molten lead bromide. Lead is deposited at cathode.<\/p>\n

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