Question List: Classification of Elements-Periodic Table

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                    Topic: Classification of Elements-Periodic Table

  1. Name any 2 elements which are
    1. metals.
    2. non-metals.
    3. semi-metals.
  2. Why do we classify elements?
  3. State Law of Triads.
  4. Check if the given elements form a Triad-  Ca, Sr and Ba.                                       Atomic Weight- Ca: 40, Sr: 88 and Ba: 137.
  5. Check if the given elements form a Triad- Cl, Br and I.                                               Atomic Weight- Cl:35.5, Br:80 and I:127.
  6. What are the limitations of Law of Triads.
  7. Check if the given elements form a Triad- F,Cl, and Br.                                               Atomic Weight- F:19, Cl:35.5 and Br:80.
  8. What relation did Dobereiner wanted to establish between elements?
  9. State Law of Octaves.
  10. X and Y are two elements having similar properties which obey Newland’s law of octaves. How many elements are there in between X and Y?
  11. What are the limitations of Newlands’ Octaves.
  12. How did Mendeleev explain the similarity amidst elements in the same group.
  13. State Mendeleev’s Periodic Law.
  14. How did Mendeleev predict the property of missing elements?
  15. Name 2 elements that exist in liquid state at room temperature.
  16. How did Mendeleev correct the atomic weight of Be.
  17. Why did Mendeleev leave some gaps in his periodic table?
  18. What are the limitations of Mendeleev’s Table?
  19. What is your understanding of Ea2O3, EsO2.
  20. How do properties of eka-aluminium predicted by Mendeleev compare with the actual properties of Gallium?
  21. What is Modern Periodic Law.
  22. In Modern Periodic Law, what is common for elements belonging to the same group? What is common for elements belonging to the same period?
  23. How is group number related to valency of an element?
  24. Why are lanthanides and actinides placed at the bottom of the periodic table?
  25. Why are there only 8 elements in third period?
  26. List elements belonging to
    1. Alkali Family
    2. Chalcogen Family
  27. f-block elements are also known as _____.
  28. d-block elements are also known as ______.
  29. How does valency vary down the group, across the period?
  30. Comment on the placement of Hydrogen in the periodic table.
  31. Element A has the electronic configuration 2, 8, 5.
    1. What is the atomic number of this element?
    2. To which element would element A be chemically similar- N or F or Ne?
  32. Atomic number of elements A, B, C, D are equal to 13, 12, 11 and 10, respectively. Which element does not belong to this set.
  33. Electronic configuration of Element X : 2; Element Y: 2,6 and Element Z : 2,8,2
    1. Which element belongs to second group?
    2. Which element belongs to second period?
    3. Which element belongs to Noble gas group?
  34. If two elements have the same valence shell, then the elements belong to ______ in the periodic table.
  35. The period number of an element is equal to the number of _____ in its atom.
  36. If two elements have the same valency, then the elements belong to _____ in the periodic table.
  37. Define the following periodic property
    1. Atomic radius
    2. Ionisation energy
    3. Electron Affinity
    4. Electronegativity
  38. According to Pauling electronegativity depends on ____.
  39. Why F has lesser electron affinity than Cl?
  40. Why does atomic radius decrease across the period even though the principal energy shell remains the same?
  41. Which atom is bigger, Na or Mg?
  42. F, Cl and Br are elements each having seven electrons. Which of these a) has the largest atomic radius b) is most reactive? State reasons.
  43. Why do elements in the same group have similar properties?
  44. An element has atomic number 11. Identify its group. Is the element metal or non-metal?
  45. The calculated electron affinity for noble gases is positive. Explain.
  46. C, N, O. Which among this has higher ionisation energy?
  47. How is atomic radius estimated?
  48. Between Na and Na+ would have more size? Why?
  49. An element X belongs to 3rd period and 2nd group of the periodic table. State:
    1. number of valence electrons
    2. valency
    3. metal or non-metal
    4. name of the element
  50. A metal X is in the first group of the periodic table. What will be the formula of its oxide? What will be the formula of its chloride?
  1. How do you appreciate the effort of Mendeleev in constructing his periodic table?
  2. How does the position of elements in periodic table help you in predicting its chemical properties?
  3. Define Ionisation energy. Explain the factors that influence Ionisation energy.
  4. How does electron affinity vary a) across the period b) down the group? List the factors that influence electron affinity.
  5. State Modern periodic law. What is your understanding of the construction of modern periodic table?

Atomic Structure-Question List

Short Questions (1 or 2 marks)

  1. What is absorption spectrum?
  2. What is emission spectrum?
  3. The circular paths in which electrons revolve are called _____
  4. Why are light rays called as electromagnetic waves?
  5. Write Planck’s equation. What is its significance?
  6. What do you observe on heating an iron rod?
  7. Red colour has ____ wavelength compared to blue colour.
  8. What is a continuous spectrum? Give example.
  9. What is a line spectrum?
  10. Why do street lamps give yellow colour light?
  11. Speed of light in vacuum is ____
  12. K shell has ____ subshell
  13. If n = 2, write l = ? and m = ?
  14. Write the four quantum numbers for the electron in H-atom.
  15. Write the 4 quantum numbers for the electron entering the last orbital of Na atom.
  16. ___ is the maximum number of electrons that can be accommodated in d-orbital.
  17. While writing electronic configuration for F, a student wrote 1s2 2s1 2p6. Is this correct?
  18. While writing electronic configuration of Sc, a student wrote 1s2 2s2 2p6 3s2 3p6 3d3. Is this correct?
  19. An electron has the following four quantum numbers. n=2, l=0, m=0, s=1/2. To which orbital does the electron belong?
  20. What is the importance of nlx method of writing electronic configuration?
  21. Draw p-orbitals.
  22. Draw dx2-y2, dz2, dxy orbitals.
  23. What are degenerate orbitals?
  24. Do 2p and 3p orbitals have the same energy?
  25. Write electronic configuration for a) S  b) Mg  c) Fe  d) N
  26. What is Heisenberg’s uncertainty principle?
  27. Define an orbital.
  28. How did Sommerfeld modify Bohr’s atomic model.
  29. Wavelength of violet light is 400 nm. What is its energy?
  30. A student made a paste of the following salts in mineral acids and introduced to flame. Guess the colour of the flame observed for each of the salts given below
    • KCl
    • CuSO4
    • CaSO4
    • SrCl2

4 marks Questions 

  1. Write the rules to be followed while writing electronic configuration.
  2. What is the importance of writing electronic configuration?
  3. Explain briefly on the four quantum numbers.
  4. Explain on Bohr’s model of Hydrogen atom?
  5. Discuss the various regions of electromagnetic spectrum.

Chemical Equations- Question List

Short Q&A (2 or 1 marks)

  1. What is the difference between physical change and chemical change?
  2. How do we know that a chemical reaction has taken place?
  3. What happens when CaO is treated with water?
  4. What temperature changes do you observe when CaO is treated with water?
  5. Give an example for precipitation reaction.
  6. On mixing Zn granules with an acid, which gas is released? How would you test it?
  7. What are reactants?
  8. What are products?
  9. What is a chemical equation?
  10. What is a balanced chemical equation?
  11. Why should chemical equation be balanced?
  12. While white washing of walls, an aqueous solution of calcium hydroxide is painted on the wall. A couple of days later, why does the wall turn white?
  13. What is meant by endothermic reaction?
  14. In a chemical equation, what does an upward arrow indicate?
  15. What does coefficients in a balanced chemical equation indicate?
  16. What is meant by limiting reagent?
  17. 1 mole of any gas occupies ___ volume
  18. What is a skeleton equation?
  19. What does the symbol (aq) represent in a chemical equation?
  20. What is wrong in the following chemical equations. Correct it.
    • H2 + O —-> H2O
    • Ca(OH) + CO2  —-> Ca(CO3) + H2O
  21. Why is respiration considered as an exothermic reaction?
  22. On adding dil.HCl to copper oxide, the solution formed is blue-green. Write the name and molecular formula of the new compound formed.
  23. Why is photosynthesis considered an endothermic reaction?
  24. Complete the following reaction
    • Pb(NO3)2 + 2KI —-> ______ + ______
    • Cu2S + O2 —–> ______ + _______
  25. Write a chemical equation for the following reactions
    1. Magnesium ribbon is heated in presence of air, producing white flame and forms white powder called Magnesium Oxide.
    2.  Sodium metal reacts with water to form sodium hydroxide and the hydrogen gas.

Balance the following equations

  • Na + O2 —> Na2O
  • H2O2 —.> H2O + O2
  • BaCl2 + H2SO4 —> BaSO4 + HCl
  • Fe + O2 —> Fe2O3
  • Al2(SO4)3 + NaOH —> Al(OH)3 + Na2(SO4)
  • Al + CuCl2 —> AlCl3 + Cu
  • Al(OH)3 —-> Al2O3 + H2O
  • N2 + H2 —> NH3
  • KClO3 —-> KCl + O2
  • MnO2 + HCl —-> MnCl2 + Cl2 + H2O
  • C3H8 + O2 —-> CO2 + H2O
  • SO2 + O2 —-> SO3
  • Cu(SO4) + NaOH —-> Cu(OH)2 + Na2SO4
  • Pb(NO3)2 —-> PbO + NO2 + O2
  • FeSO4 —-> Fe2O3 + SO2 + SO3

4 Marks Q&A

  1. What information do you obtain from a balanced chemical equation? Explain with examples.
  2. Heat is liberated in the reactions where water was added to Calcium Oxide and when Hydrochloric acid is added to Zinc granules. Ramu said as heat is liberated, both reactions are of the same type. Eswar was of the opinion that both reactions are different. Who do you think is correct? Write equations and explain.
  3. Write the steps involved in balancing a chemical equation. Elucidate.
  4. X is a brown shining element with atomic number one unit greater than Ni. When X is burnt in air, it turns black. Wat is X? What is the new substance?
  5. When the solution of substance X is added to a solution of KI, then a yellow solid is formed as precipitate is formed. What is X? Name the new substance formed. Write the chemical equation.
  6. A metal Y forms a salt YSO4. When the aqueous solution of the salt YSO4 is treated with NaOH, a blue precipitate is formed. Metal Y is used in making electrical wires and alloys like brass. What is the metal Y. Identify the blue precipitate. Write the chemical equation.


Atomic Weight:

H = 1 U  C = 12 U  N = 14 U  O = 16 U  Na = 23 U  Mg = 24 U  Al = 27 U  Cl = 35.5U  K = 39 U  Ca = 40 U  Fe = 56 U

  1.  Al + Fe2O3 —> Al2O3 + Fe. Calculate the amount of Aluminium required to form 616g of iron.
  2. Calculate the volume of Hydrogen gas liberated when 276 g of sodium reacts with water.
  3. Calculate the number of molecules of CO2 liberated when 50g of CaCO3 is treated with 7.3g of HCl. Which is the limiting agent?
  4.  92g of Na contains ____ number of Na atoms.
  5.  32g of oxygen gas occupies ____volume.
  6. 47g of impure Al2O3 is reduced electrolytically to give Aluminium and Oxygen. Calculate the amount of Aluminium formed.
  7. C2H6 + O2 —-> CO2 + H2O. 60 litres of ethane (C2H6) is mixed with 448 litres of oxygen (O2) and ignited. Calculate the volume of CO2 formed during this reaction.
  8. How many moles of water are required to be dissociated to produce oxygen gas which is sufficent to form 800g of MgO by burning Mg with oxygen.
  9. Calculate the amount of KCl formed when 12.25g of KClO3 is decomposed.
  10. What is the amount of NH3 formed when 14g of N2 reacts with 6g of H2.

TS Physical Science Answer Key SSC 2017

Section – I

1. Ag, Fe, Zn, Na

2. Change the poles of the magnet or wire

3. n = 4, l= 0 , m = 0, s = 1/2

4.  Person develops Myopia. Person can see nearby objects but not distant objects.



6. We can’t use the same wire as fuse wire. Fuse wire needs to have low melting point in order to break the circuit during overload.



Section – II

8. Al + Fe2O3 –> Al2O3 + Fe

Aluminium is a more reactive metal. It reduces iron oxide (hematite) to iron.


IMG_20170325_185111Electrons are arranged from lower energy level to higher energy level(Aufbau Principle).

There cannot be more than 2 electrons in an orbital. No two electrons can have all 4 quantum numbers same(Pauli’s Principle)

Degenerate orbitals should be half-filled before pairing up electrons.(Hund’s Rule)



11. (i) Substance C can be neutral.

(ii) Substance B is basic, with phenolphthalein, it will turn pink in colour

12. Any object(light source) kept at the centre of curvature will give inverted image of the same size (as that of the object) on a screen at the centre of curvature. Place a candle at a certain distance from lens. Adjust the screen such that an inverted same size image is obtained. Now, distance between lens and screen is radius of curvature. Half of the radius will give focal length value.

13. Convex lens: Boy is trying to see moon. When object is at infinity, the image is formed at the focus. As both the lenses have same focal length and are separated by a distance of 2f, the image formed by the first lens, becomes the object for the second lens. Thus, for the second lens, object is at its Focus. The boy would see a highly enlarged image of the moon.

Section – III

14. Chemical Equation

Zn + 2 HCl –> ZnCl2 + H2

In the balanced chemical equation, 2 moles of HCl gives 1 mole of H2. If we use, 1 mole of HCl, we would get 0.5 moles of H2.


1 mole of H2 = 6.023×10^23 molecules

Hence, 0.5 moles of H2 = 3.012 x 10^23 molecules

14. Electron Affinity

Definition : Energy released from a neutral gaseous atom when it accepts an electron in its valence shell.

Factors Affecting E.A: Atomic Radius, Effective Nuclear Charge, Screening Effect, Electronic configuration.

Atomic radius: More the atomic radius, lesser is the Electron affinity.

Effective Nuclear Charge is weaker when the valence shell electrons are being located farther away from the nucleus. Lesser the effective nuclear charge, lesser is the electron affinity

Screening Effect is more when there are lots of inner shell electrons. If more inner shells electrons are present, they screen or shield and hence decrease nuclear attraction over valence electrons. More screening effect, less electron affinity.

Electron affinity is lesser if the element has either half-filled electronic configuration and E.A is almost zero if the element has fully-filled  electronic configuration.

15. Hypermetropia and Correction

Person with this defect cannot see nearby objects. 

Near Point – The nearest distance at which the lens can form an image on the retina or the minimum distance beyond which a person with hypermetropia can see an object.


        • Person with Hypermetropia can see at & beyond Near Point.
        • Person cannot see from 25 cm to Near Point.
        • In order to correct Hypermetropia, we should use a lens that can form the image at or beyond near point for an object located within the near point.
        • Biconvex lens is suited for this purpose.


  • object distance, u = -25 cm
  • image distance, v = near point distance, -d
  • Lens Formula:
    • 1/f = 1/v – 1/u
    • 1/f = -1/d – (-1/25)
    • 1/f = -1/d + 1/25
    • 1/f =  -25+d / 25d
    • f = 25d/d-25
    • As, d is more than 25 cm, focal length will be positive value.

15. Current carrying wire in a magnetic field

When a current carrying wire is placed perpendicular to the magnetic field, a mechanical force is exerted on the conductor.

F = q v b sin(theta)

Direction of movement of the conductor is given by Fleming’s Left Hand Rule.

Fore finger, Middle finger and Thumb of the left hand are held at right angles to each other. Fore finger is aligned with the direction of magnetic field, Middle finger points to the direction of current, then the direction in which thumb points, gives the direction of force on the conductor.


  • Suspend a copper wire AB vertically from a support.
  • Lower end B of the wire should touch the surface of mercury kept in a vessel.
  • Positive terminal of a battery is connected to end A of the wire.
  • Circuit is completed by dipping another wire from negative terminal of battery into the mercury vessel
  • The entire set is placed perpendicular to a uniform magnetic field using horse shoe magnet
  • When current passes through the wire from A to B and magnetic field lines are from left to right, then the wire AB moves in the forward direction. Lower end B moves to new position B’, thus in the circuit, connection is broken.
  • Since no current flows in the wire’s new position, mechanical force is not exerted and wire reverts to its original position. Wire makes contact with mercury and current starts to flow in the wire and wire moves forward.
  • This motion is repeated until battery gets drained.
  • If we reverse, the direction of current, then the wire moves in rear direction.

16. Acids/ Bases have ions

Materials Required: HCl, H2SO4, Acetic acid, Citric acid, NaOH, KOH, NH4OH, Glucose, Alcohol, Graphite Rods, AC plug-220V, Bulb, Electrical wires.


      • Prepare solutions of HCl, H2SO4, Citric acid, Acetic acid,NaOH, KOH, and NH4OH, Glucose, Alcohol.
      • Take a beaker and add HCl solution.
      • Insert 2 Graphite rods into the solution.
      • Connect one of the rod to the AC plug, Connect the other rod to the bulb. Complete the circuit by connecting bulb and AC plug. Use electrical wires for connecting.
      • Switch on the current.
      • Repeat the same procedure for H2SO4, Citric acid, Acetic acid,NaOH, KOH, NH4OH, Glucose and Alcohol


      • Light bulb glows for all the solutions, except glucose and alcohol.
      • Dim glow is seen for acetic acid and citric acid and NH4OH.
      • Bright glow is seen for HCl and H2SO4, NaOH, KOH.
      • Glucose and alcohol does not have ions, so bulb does not glow.


      • Acids and Bases behave as electrolytes. Acids give H+ ions in solution which results in flow of current. Bases give OH- ions in solution which results in flow of current.
      • HCl, H2SO4 are strong acids, i.e., more H+ ions are produced.
      • Acetic acid and citric acid are weak acids, i.e., less H+ ions are produced.
      • Similarly, NaOH and KOH are strong bases, giving more OH- ions, whereas, NH4OH is a weak base, giving less OH- ions.

Thus, passing of current and glowing of bulb shows that acids and bases have ions.

16. Esterification

Reaction between carboxylic acid and alcohol in presence of conc.H2SO4 —> esters

Materials Required: Acetic acid, Ethanol, Conc.H2SO4, Beakers, Water, Burner, Test-tube


1 ml of ethanol is added to 1 ml of ethanoic acid, few drops of Conc.H2SO4 is added and warmed in water bath for few minutes and then poured into a test tube containing water. The resulting mixture has sweet smell. This is due to the formation of ester



17. Focal length CalculationNew Doc 2017-03-26 (1)

Metallurgy – Lesson Summary

Class 10

Physical Science

Lesson Summary: Principles of Metallurgy


  • Process of extraction and purification of metals from its ore
  • Earth’s crust is made of minerals. Metals can be extracted from minerals.
  • A mineral from which a metal can be extracted in good yield and in a cost-effective manner is called as Ore.
Ore Name Chemical Formula Ore Type Metal
Bauxite Al2O3.2H2O Oxide ore Al-Aluminium
Pyrolusite MnO2 Oxide ore Mn-Manganese
Hamatite Fe2O3 Oxide ore Fe-Iron
Magnetite Fe3O4 Oxide ore Fe-Iron
Zincite ZnO Oxide ore Zn-Zinc
Zinc Blende ZnS Sulphide ore Zn-Zinc
Cinnabar HgS Sulphide ore Hg-Mercury
Galena PbS Sulphide ore Pb-Lead ore
Epsom MgSO4.7H2O Sulphate ore Mg-Magnesium
Gypsum CaSO4.2H2O Sulphate ore Ca-Calcium
Horn Silver AgCl Chloride ore Ag-Silver
Rock Salt NaCl Chloride ore Na-Sodium
  • Metallurgical Process involves 3 steps
    • Concentration (ore is taken from crust)
    • Extraction (metal is extracted from ore)
    • Refining (pure metal is taken from impure metal)


  • Unwanted rocky materials, dust, soil, sand etc are removed from ore.
  • 4 ways to concentrate an ore
    • Hand-Picking
    • Washing
    • Froth Floatation
    • Magnetic Separation
  • Hand-Picking
    • This method is opted when the impurities have a different texture/size/colour than the ore. Ore particles are hand picked.
  • Washing
    • This method is opted when impurities are smaller/less denser than ore.
    • Ore is kept on an inclined plane surface and washed with water.
    • Impurities are washed with water, leaving the ore concentrated.
  • Froth Floatation
    • This method is used for sulphide ores.
    • Powdered ore is added in a floatation cell containing water and few drops of pine oil.
    • Compressed air is passed into the floatation cell.
    • Ore particles along with froth raise to the top of the cell, while impurities (gangue) settle at the bottom of the cell.
  • Magnetic Separation
    • This method is used for ores that have magnetic property (Eg: iron ore)
    • Powdered ore is passed on a moving belt running across 2 wheels. One of the wheel is magnetic and the other is non magnetic.
    • Magnetic ore particles are attracted towards the magnetic wheel.


  • Extraction methods are chosen depending on the reactivity of the metal.
Reactivity Example Method of extraction
Highly Reactive Na, K, Mg, Ca, Al Electrolysis
Moderately Reactive-Sulphate ore and Sulphide ore Fe, Cu, Zn, Pb Roasting + Reduction
Moderately Reactive-Carbonate ore Fe, Cu, Zn, Pb Calcination + Reduction
Less Reactive Ag, Au, Hg Roasting + Reduction


  • Extraction of Highly Reactive Metals
  • Electrolysis:-
    • For highly reactive metals, reduction method of extraction is not economically viable.
    • Electrolysis is done with molten (fused) ore. Electrolysis of aqueous solution is not preferable because ions from water will be discharged at the cathode.
    • Process
      • Extraction of Sodium from Rock Salt
      • Cathode: Steel
      • Anode: Graphite
      • Electrolyte: NaCl fused ore
      • On passing electricity, electrolysis occurs.
        • At the Cathode: Sodium ion gets an electron and deposits as Sodium metal
        • At the Anode: Chlorine ions combine to form Chlorine gas. Each Chlorine ion gives off 1 electron.
      • Suitable impurities, if needed, are added to the ore to decrease the melting point.


  • Extraction of Moderately Reactive Metals
  • Roasting:-
    • Pyrochemical process
    • Heating sulphide ores in presence of oxygen
    • Metal oxide is obtained




  • Calcination:-
    • Pyrochemical process
    • Heating carbonate ores in the absence of oxygen
    • Metal oxide is obtained



  • Reduction:-
    • The metal oxides obtained from roasting or calcinations are reduced to their corresponding metals
    • Reduction with carbon
      • Usually done for metals like – Zn, Fe, Ni, Sn, Cu, Pb





  • Reduction with other metals
    • More reactive element can reduce a metal oxide by displacing the metal from its oxide.
    • Aluminum – more reactive metal when compared to Zn, Mn, Cr, Fe. Aluminum powder is used as reducing agent.
    • Using Aluminum to reduce metal oxides is a highly exothermic reaction. This reaction is called Thermite reaction, because both Heat and Al2O3 (bauxite) are formed.
    • Thermite reaction
      • A mixture of iron oxide, Fe2O3 and Al powder is heated in presence of Mg ribbon.
      • Al reduces iron oxide to give Fe, Heat and Al2O3. Heat produced is high enough to melt the iron
      • Molten iron, so produced, is used to join railings of tracks or cracked machine parts – thermite welding
    • Auto Reduction
      • Certain sulphide ores (Cu2S) are roasted partially
      • On further heating, Cu2S and Cu2O react together to from metal and SO2



  • Extraction of Less Reactive Metals
  • Roasting and Reduction by heating
    • Mercury ore (HgS) is heated to from HgO, which on heating is reduced to Hg



  • Treating with KCN
    • Silver sulphide is treated with KCN to form potassium silver cyanide. When Zinc dust is added to potassium silver cyanide, it gives Ag



  • Metals obtained from extraction process contain some impurities. Refining of impure metals is called Purification
  • Distillation
    • Purification of low boiling metals – Zn, Hg
    • Impurities – High boiling
    • Extracted metal is distilled to obtain pure metal
  • Liquation
    • Purification of metals with low melting point– Sn
    • Impurities – High boiling
    • Extracted are metals are heated and pure metal is collected from a sloppy surface
  • Poling
    • Molten metal is stirred with poles of wood
    • On heating, impurities get converted to gases or get oxidized and form as removable slag over the molten metal.
  • Electrolytic Refining
    • Usually done for metals like Cu, Zn, Sn, Pb, Cr, Ni, Ag, Au
    • Thick block of impure metal = Anode
    • Thin strip of pure metal = Cathode
    • Aqueous solution of the corresponding metal salt = Electrolyte
    • On passing electric current, metal from anode goes into solution, metal from electrolyte deposits at cathode
    • Soluble impurities from anode goes into solution, insoluble impurities from anode, deposit at the bottom of the anode. This is called anode mud.
    • Anode mud contains valuable metals like Sb, Te, Se, Ag, Au
    • Electrolytic Refining of Copper
      • Acidified Copper sulphate solution, i.e., CuSO4 + H2SO4 + H2O = electrolyte
      • Impure copper metal = Anode, i,e., connected to positive terminal of battery
      • Pure copper metal = Cathode , i,e., connected to negative terminal of battery
      • On passing electric current, impure Cu from anode goes into CuSO4 solution, pure Cu2+ from CuSO4 gets deposited at cathode as Cu
      • As the process goes on, anode thickness decreases and anode thickness increases. Pure copper is obtained at the cathode.
      • Cathode reaction


  • Anode reaction



  • Reactive metals like copper, iron, silver gets oxidized in the presence of moisture and O2
  • Reddish brown dust –Hydrated Iron oxide; Green coating on copper – Copper carbonate; Blackening of silver – Silver sulphide
  • Corrosion of iron is rusting
    • Rusting occurs in the presence of both moisture and O2
      • When iron nail is kept in a test tube with water and oil = no rusting
      • When iron nail is kept in a test tube with dry air and dry CaCl2 = no rusting
      • When iron nail is kept in a test tube with water and air = rusting
    • Corrosion is an electrochemical process
      • Anode = where oxidation of Fe occurs


  • Cathode = reduction of oxygen occurs in the presence of H+ ion. This is done by the electrons released from anode



  • Overall Reaction


  • Fe2+ is further oxidized to Fe3+ which forms hydrated iron oxide


  • Prevention of Corrosion
    • By painting
    • By applying grease or oil
    • By galvanization – electroplating zinc on iron objects.
    • By tin or chromium plating
    • By alloying
      • Alloy is a homogenous mixture of two or more metals.
      • Iron is alloyed with Cr and Ni to obtain stainless steel.
      • Alloys are generally stronger than the metals from which they are made; more resistant to corrosion; have lower electrical conductivity than pure metals and improved properties than pure metals.
      • Other common alloys
        • Gold + Silver or copper = 22 carat gold
        • Copper + Zinc = Brass
        • Mercury + other metals = Amalgam


  • Smelting
    • Ore is mixed with flux and fuel and heated strongly
    • Flux is a substance added to remove impurities (gangue) from ore.
    • If gangue is acidic, flux is basic and vice versa
    • During smelting, gangue and flux react to form a removable substance called slag










  • Furnace
    • Pyrochemical process is carried out in furnace.
    • Furnace has 3 parts – Hearth, Chimney, Fire Box
    • Ore is kept at hearth of the furnace
    • Fuel is kept in fire box
    • Waste or gases go out of the chimney
    • Types of furnace – Reverberatory furnace, Blast furnace, Retort furnace
    • Blast furnace
      • Fire box an hearth are combined in a big chamber
      • Haematite ore is smelted in blast furnace
    • Reverberatory furnace
      • Fire box an hearth are kept in separate chambers
      • Vapours from the burning fuel touch the ore and heat it.
    • Retort furnace
      • Fire box an hearth are kept in separate chambers
      • Flames of the fuel do not touch the ore.