Electrolysis Class-10 Goyal Brothers ICSE Chemistry Solutions Ch-6. Step by Step Goyal Brother Prakashan Chemistry Solutions of Exercise and Objective Type Questions Chapter-6 Electrolysis for ICSE Class 10 . Visit official Website CISCE for detail information about ICSE Board Class-10 Chemistry .
Electrolysis Class-10 Goyal Brothers ICSE Chemistry Solutions Ch-6
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Exercise Page-118 to 119
Electrolysis Class-10 Goyal Brothers ICSE Chemistry Solutions Ch-6
Question 1.
(a) What do you understand by the following terms
(i) electrolyte,
(ii) non-electrolyte?
(b) Pick out electrolytes and non-electrolytes from the following :
(i) sugar solution
(ii) dilute sulphuric acid
(iii) fused lead bromide
(iv) solution of sulphur in carbon disulphide
(v) aqueous sodium chloride solution,
(vi) solid potassium chloride
(vii) ethyl alcohol
(viii) acidulated water
(ix) caustic soda solution (x) petrol.
Answer :
(a)
(i) electrolyte-An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent
(ii) non-electrolyte- a substance that does not readily ionize when dissolved or melted and is a poor conductor of electricity.
(b) electrolytes and non-electrolytes :
(i) sugar solution– non-electrolyte
(ii) dilute sulphuric acid–electrolytes
(iii) fused lead bromide–electrolytes
(iv) solution of sulphur in carbon disulphide–Non electrolytes
(v) aqueous sodium chloride solution, –electrolytes
(vi) solid potassium chloride- — non-electrolyte
(vii) ethyl alcohol— non-electrolyte
(viii) acidulated water–electrolytes
(ix) caustic soda solution–electrolytes
(x) petrol.– non-electrolyte
Question 2. What do you understand by the following terms :
(a) electrolysis, (b) electrode, (c) cathode, (d) anode, (e) cation, (f) anion, (g) voltameter ?
Answer :
(a) electrolysis– ,A process in which a chemical change, especially decomposition, is brought about by passing an electric current through a solution of electrolytes so that the electrolyte’s ions move toward the negative and positive electrodes and react with them.
(b) electrode,-An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air)
(c) cathode-A cathode is the electrode from which a conventional current leaves a polarized electrical device.
(d) anode- An anode is an electrode through which the conventional current enters into a polarized electrical device. This contrasts with a cathode, an electrode through which conventional current leaves an electrical device. A common mnemonic is ACID, for “anode current into device
(e) cation-a positively charged ion that is attracted to the cathode in electrolysis. any positively charged atom or group of atoms (opposed to anion)
(f) anion- a negatively charged ion, as one attracted to the anode in electrolysis. any negatively charged atom or group of atoms (opposed to cation)
(g) voltammeter – A method of determining the chemical makeup of a sample substance by measuring electrical activity, or the accumulation of chemicals, on electrodes placed in the substance.
Question 3. Pick out the cations and anions from the following:
(i) SO42- (ii) Pb+2 (iii) NH+4 (iv) OH- (v) NO3- (vi) H+ (vii) Ag+ (vii) Cu2+ (ix) CN – (x) Cl-
Answer :
(i) SO42- — anions
(ii) Pb+2 — cations
(iii) NH+4 — cations
(iv) OH- — anions
(v) NO3- — anions
(vi) H+ — cations
(vii) Ag+ — cations
(vii) Cu2+ — cations
(ix) CN – — anions
(x) Cl- — anions
Question 4. Fill in the blanks.
(i) The metal plate through which current enters into an electrolyte is called _________. It has _______ of electrons.
(ii) The metal plate through which ________ leaves an electrolyte is called . It has __________ of electrons.
(iii) The ions which discharge on the negative electrode during electrolysis are________ electrons. Thus the ions are said to be __________.
(iv) The ions which discharge on the positive electrode during electrolysis are ___________ electrons. Thus the ions are said to be ___________ .
(v) Hydrogen and metallic ions are _________ , because they are __________ electrons.
(vi) Non-metallic ions are __________ because they are __________ electrons.
Answer :
(i) The metal plate through which current enters into an electrolyte is called _____Anode____. It has __Lack_____ of electrons.
(ii) The metal plate through which ____Current____ leaves an electrolyte is called . It has ____excess______ of electrons.
(iii) The ions which discharge on the negative electrode during electrolysis are____gain____ electrons. Thus the ions are said to be __cation________.
(iv) The ions which discharge on the positive electrode during electrolysis are _____loose______ electrons. Thus the ions are said to be ____anion_______ .
(v) Hydrogen and metallic ions are ___cation______ , because they are ______lack____ electrons.
(vi) Non-metallic ions are _____electronegative_____ because they are _______gain___ electrons.
Question 5.
(a) What do you understand by the term “electrolytic dissociation'”?
(b) The dissociation of sodium chloride solution in water is 99%. What do you mean by the statement?
Answer
(a) electrolytic dissociation-In electrolytic, or ionic, dissociation, the addition of a solvent or of energy in the form of heat causes molecules or crystals of the substance to break up into ions (electrically charged particles). Most dissociating substances produce ions by chemical combination with the solvent
(b) It means that NACL when dissolved in water gets dissociated and can be used as an electrolyte and it allows 99% of current through it
Question 6. Solid sodium chloride is a bad conductor of electricity. However, fused sodium chloride conducts electric current. Explain on the basis of the theory of ionisation.
Answer :
1. In solid sodium chloride there is the force of attraction between the two atoms as they form the ionic bond by sharing of electrons .Therefore as a result there is no flow of electricity.
2.In case of molten sodium chloride the atoms dissociate and form ions .As a result there are free electrons which are required to the flow of electricity . Therefore molten sodium chloride conduct electricity
Question 7. How does lead bromide ionise in water when water is a polar covalent compound?
Answer :
Rather, compounds with covalent bonds dissolve in water. The water surrounds the polar sites of the molecules at the interface with the solute (whether it is a solid, a liquid, or a gas) and strips the molecules away. … The solvent particles must move apart to make room for solute particles
Question 8. By giving at least four examples, define or explain the meaning of (a) strong electrolyte (b) weak electrolyte, (c) non-electrolyte.
Answer :
(a) strong electrolyte —
HCl, HBr, , HNO3, HClO3, HClO4, and H2SO4 NaOH, KOH, LiOH, Ba(OH)2, and Ca(OH)2 NaCl, KBr, MgCl
(b) weak electrolyte-HF, HC2H3O NH3 (ammonia),
(c) non-electrolyte.- A common example of a nonelectrolyte is glucose, or C6H12O6. Glucose (sugar) readily dissolves in water, but because it does not dissociate into ions in solution, it is considered a nonelectrolyte; solutions containing glucose do not, therefore, conduct electricity. “nonelectrolyte.” “solute
Question 9. Pick out strong electrolytes and weak electrolytes from the following aqueous solutions :
(i) copper sulphate,
(ii) carbonic acid,
(iii) limewater,
(iv) sodium hydroxide,
(v) sodium carbonate,
(vi) nitric acid,
(vii) lead nitrate
Answer :
(i) copper sulphate,–strong electrolytes
(ii) carbonic acid,–weak electrolytes
(iii) limewater,—strong electrolytes
(iv) sodium hydroxide,–strong electrolytes
(v) sodium carbonate,–strong electrolytes
(vi) nitric acid,–strong electrolytes
(vii) lead nitrate.–strong electrolytes
Question 10. Write all the ions present in aqueous solutions of the following :
(i) caustic potash,
(ii) acetic acid,
(iii) magnesium sulphate,
(iv) acetic acid,
(v) phosphoric acid,
(vi) NH4Cl solution.
Answer :
(i) caustic potash, K+ ion OH- ion
(ii) acetic acid, CH3COO- and H+ ion
(iii) magnesium sulphate, SO4- and Na+ ion
(iv) acetic acid,
(v) phosphoric acid, PO4- and H+ ion
(vi) NH4Cl solution. Cl- and NH4+ ion
Question 11.
(a) Al3+ : Cu2+ ; Na+ ; Zn2+ ions are present in an aqueous solution, such that the concentration of ions is the same. Write the order of discharge of ions.
(b) Amongst the OH ions and Br ions which are likely to discharge first?
Answer :
(a )The order of discharge of ions is Al+3 ,Cu+2 ,Na+ ,Zn+2 because as the concentration is same, an ion placed lower in electrochemical series get preferentially discharged.
(b )OH– is likely to discharge first in comparison to Br– ions
Question 12. By giving an example, explain how nature of the anode changes the preference of discharge of anions.
Answer :
Nature of the Electrode: This is not as important as either of the other two factors, except in certain cases. For example in the electrolysis of molten sodium chloride using a mercury cathode, sodium ions are discharged in preference to hydrogen ions which are lower in the series.
Question 13. By writing ionic reactions at the cathode and anode, describe electrolysis of water using platinum electrodes
Answer :
Electrolysis of water is the process of using electricity to decompose water into oxygen and hydrogen gas. Hydrogen gas released in this way can be used as hydrogen fuel, or remixed with the oxygen to create oxyhydrogen gas, which is used in welding and other applications
During electrolysis of water,
At anode:
At cathode:
Question 14. Describe electrolysis of copper sulphate using copper electrodes.
Answer :
Electrolysis of Copper sulphate solution
Electrolyte: Dilute copper sulphate solution
Anode: Copper electrode
Cathode: Copper electrode
#Note: Copper electrodes are active electrodes.
Dissociation reaction:
CuSO4 ————-Cu2+ + SO42-
Copper sulphate Cation Anion
Discharge of Ions at Electrodes
At Cathode (Negative electrode) |
At Anode (Positive electrode) |
Positively charged ions (cations) get attracted to the cathode and gain electrons from it to form neutral atom. i.e, Cu atom [metal]. | Negatively charged ions (anions) get attracted to the anode and lose electrons from it to form neutral atom. i.e, Cu ions.
The electrode used is copper electrode (anode) which is an active electrode and hence takes part in the electrolytic reaction. |
Reaction at cathode:
Cu2+ + 2e ̶ → Cu Cation Electrons Metal |
Reaction at anode:
Cu2+ ̶ 2e̶ → Cu2+ Copper Electrons Ions Anode SO42- and OH- are not discharged. |
Product formed at cathode:
The blue copper ions are discharged as copper atoms [metal] at the cathode. |
Product formed at anode:
The copper (anode itself) ionizes to give copper ions at the anode. Anode thus gets transferred on to the cathode and the solution remains blue |
Question 15. Describe electrolysis of copper sulphate, using platinum anode and copper cathode. Describe your observations, if current is passed for a long time.
Answer :
In the aqueous solution, copper sulphate dissociates into its respective ions. On passing electric current, the copper ions (cations) move towards the cathode and get deposited as copper. Simultaneously, the sulphate ions (anions) move towards the anode. So, blue colour of the solution disappears
Question 16. Briefly describe electrolysis of lead bromide using graphite electrodes.
Answer :
The half-equations for the electrolysis of lead(II) bromide. This is a reduction reaction because the lead ions gain electrons. The negative bromide ions are attracted to the positive anode electrode and discharged to form bromine vapour. This is an oxidation reaction because the bromide ions lose electrons
Question 17.
(a) What do you understand by the term “electroplating”?
(b) Why do we electroplate certain articles?
(c) By drawing a neat diagram write the reactions which take place at the cathode and anode during silver plating.
Answer :
(a)
The process of coating the surface of a conducting material with a metal. During the process, the surface to be covered acts as a cathode in an electrolytic cell, and the metal that is to cover it acts as an anode. Electroplating is usually used to cover a less expensive metal with a more expensive metal, or to cover a corrosive metal with a less corrosive or noncorrosive metal.
(b)
Electroplating is widely used in industry and decorative arts to improve the surface qualities of objects—such as resistance to abrasion and corrosion, lubricity, reflectivity, electrical conductivity, or appearance.
(c)
Anode : A plate or rod of silver. (ii) Sodium argento cyanide (Na[Ag(CN)2]) and hydrocyaruc acid (HCN). (v) Overall strength of silver ions does not change in the electrolyte as the number of Ag+ ions entering the electrolyte is equal to the number of Ag+ ions discharged at cathode.
Question 18. State four precautions taken during electroplating.
Answer :
(1) The articles to be plated should be cleaned thoroughly to remove dust, grease or any deposit on it.
(2) Only direct current should be used.
(3) The temperature around the electroplating equipment should be optimum..
(4) The articles to be plated should be cathode
Question 19. How can impure copper be purified by electrolytic method? What happens to the impurities present in copper?
Answer :
Copper is purified by electrolysis. In this process copper is transferred from an impure anode to the cathode of an electrolytic cell. The insoluble impurities fall to the bottom. The copper produced by this process is 99.99% pure copper.
Question 20. How can electrolysis be used in the extraction of aluminium? Why can aluminium not be reduced by conventional reducing agents?
Answer :
aluminium is extracted from its oxide by electrolytic reduction and not by the conventional reducing agent. … Also, Al-O bond is extremely strong and requires high energy to break which requires very high temp. (above 2000 C) which is difficult to maintain hence electrolytic reduction method is easier and cheaper
Question 21. With respect to electrical properties, give two differences between an electrolyte and a metal.
Answer :
Metallic conductance involves the movement of electrons throughout a metal. Electrolytic conduction involves the movement of ions throughout a pure liquid or solution. The major difference between them is that one involves the movement of electrons and the other involves the movement of ions.
Question 22. State three differences between an atom and an ion
Answer :
Atoms vs. Ions. Atoms are neutral; they contain the same number of protons as electrons. By definition, an ion is an electrically charged particle produced by either removing electrons from a neutral atom to give a positive ion or adding electrons to a neutral atom to give a negative ion.
Question 23. Potassium (at. no. 19) and chlorine (at. no. 17) react to form a compound potassium chloride. Explain above reaction, on the basis of electron concept:
(a) Oxidation
(b) Reduction
(c) Oxidising agent
(d) Reducing agent.
Answer :
i) Potassium undergoes oxidation as it loses an electron and forms a cation.
(ii) Chlorine undergoes reduction as it gains an electron and forms chloride anion.
(iii) Potassium acts a reducing agent and gets oxidised.
(iv) Chlorine acts an oxidizing agent and gets reduced
Question 24. Fe+S ——–> Fe2+ s2-
Identify (a) oxidising agent (b) reducing agent in the above reaction.
Answer :
Fe→Fe2++2e−(oxidation)
Fe is losing electron, therefore it acts as a reducing agent.
S is gaining electrons, therefore it acts as an oxidising agent.
Question 25. 2Fe+ 3Cl2 ———–> 2Fe3+ Cl3-
In the above reaction, which substance is (a) oxidised (b) reduced, and why?
Answer :
his is an oxidation-reduction (redox) reaction:
2 Fe0 – 6 e– → 2 FeIII (oxidation)
Question 26.
(a) K+ + e ———> K
(b) Fe2+ – e ———> Fe3+
(c) Na – e- ——–> Na +
(d) S + 2e- ———–> S2-
In the above reactions where does (a) oxidation take place (b) reduction take place?
Answer :
(a) K+ + e ———> K (reduction take place)
(b) Fe2+ – e ———> Fe3+ (reduction take place)
(c) Na – e- ——–> Na + (oxidation take place)
(d) S + 2e- ———–> S2- ( oxidation take place )
Objective Type Questions Page -120 to 121
I. Multiple Choice Questions
Class-10 Electrolysis Goyal Brothers ICSE Solutions Ch-6
I Choose the correct answer from the options given below : (update soon)
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II. Fill in the blanks spaces with the choice given in brackets:
- ……………..aquous…………discharge …….. electrolysis……..
- …………chemical …….. electrolyte………….
- ………………….strong…………………
- ……………….strong………………….
- …………………electrochemical series………………
- ………….loss………………….
- ………..cathode………….two……………
- …………….platinum……………….
- ………….NaAg(CN)2……………………..
- …………………electrorefining………………
III. Choose the following list, as what matches the descriptions given below.
[Electroplating, Fused NaCl, nickel sulphate, platinum, K+, OH-, anode, silver, oxygen, cations]
1. An electrolyte used during nickel plating.
2. A gas liberated at anode during electrolysis of water using platinum electrodes.
3. The process of depositing a thin layer of superior metal over and inferior metal by the process of electrolysis
4. The material of anode during silver plating.
5. Electrolyte used in the extraction of sodium metal.
6. An inert anode used in the electrolysis of water.
7. A highly electropositive 1on.
8. An electronegative ion which can discharge with maximum ease.
9. Name of electrode deficient in electrons.
10. Name of the ions deficient in electrons.
Answer
1. An electrolyte used during nickel plating.–nickel sulphate
2. A gas liberated at anode during electrolysis of water using platinum electrodes.–oxygen,
3. The process of depositing a thin layer of superior metal over and inferior metal by the process of electrolysis- electroplating
4. The material of anode during silver plating.- Silver
5. Electrolyte used in the extraction of sodium metal.-NaCl
6. An inert anode used in the electrolysis of water.-platinum,
7. A highly electropositive 1on.- K+
8. An electronegative ion which can discharge with maximum ease.-OH-
9. Name of electrode deficient in electrons.- Anode
10. Name of the ions deficient in electrons.- Cation
–: end of Electrolysis Solutions Goyal Brothers :–
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