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2021-07-25 10:50:36 #Revision

Important Notes - Electrochemical Cells

► An electrochemical cell can convert electrical energy to chemical energy and can also convert electrical energy to chemical energy. There are two types of electrochemical cells- Galvanic cell and Electrolytic cell.

► Cathodes are usually metal electrodes. It is the electrode where reduction takes place. The cathode is the positive electrode in a galvanic cell and a negative electrode in an electrolytic cell. Electrons move into the cathode.

► A half-cell is half of an electrochemical cell (electrolytic or galvanic), where either oxidation or reduction occurs. At equilibrium, there is no transfer of electrons across the half cells. Therefore, the potential difference between them is nil.

► A salt bridge is a device used to connect the oxidation and reduction half-cells of a galvanic cell (a type of electrochemical cell). Strong electrolytes are generally used to make the salt bridges in electrochemical cells. Since ZnSO4 is not a strong electrolyte, it is not used to make salt bridges.

► Emf of a cell is equal to the maximum potential difference across its electrodes, which occurs when no current is drawn through the cell. It can also be defined as the net voltage between the oxidation and reduction half-reactions.

► Cell potential is an intensive property as it is independent of the amount of material present. Gibbs free energy is defined for an electrochemical cell and is an extensive property as it depends on the quantity of the material.

► Electrode potential is the tendency of an electrode to accept or to lose electrons. Electrode potential depends on the nature of the electrode, temperature of the solution and the concentration of metal ions in the solution. It doesn’t depend on the size of the electrode.

► The salt bridge connects the two half-cell solutions to complete the circuit of the electrochemical cell. The electrolytes of the salt bridge are generally prepared in agar-agar or gelatin so that the electrolytes are kept in a semi-solid phase and do not mix with the half-cell solutions and interfere with the electrochemical reaction.

► A salt bridge is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution. It maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium.

► A Voltaic or Galvanic cell is a type of electrochemical cell that converts chemical energy into electrical energy. Photovoltaic cells are used to convert light energy into electrical energy. An Electrolytic cell is a type of electrochemical cell that converts electrical energy into chemical energy. A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity.

► For all spontaneous chemical reactions, the change in Gibbs free energy (ΔG°) is always negative. For a spontaneous reaction in an electrolytic cell, the cell potential (E°cell) should be positive.

► In an electrochemical cell, when an opposing externally potential is applied and increased slowly, the reaction continues to take place. When the external potential is equal to the potential of the cell, the reaction stops. Once the externally applied potential is greater than the potential of the cell, the reaction goes in the opposite direction and the cell behaves like an electrolytic cell.

► Primary cells cannot be used again and again. Since there is no fluid inside, these cells are also known as dry cells. The internal resistance is high and the chemical reaction is irreversible. Their initial cost is cheap.

► A secondary battery (a series of cells) is one which can be charged, discharged into a load, and recharged many times. Nickel-cadmium cell, Lead storage cell and Mercury cell are examples of secondary cells. Leclanche cell is an example of a primary cell. Open / Comment

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2021-07-25 06:32:16 How to give the final shape to the NEET 2021 Preparation :

Firstly, eliminate the stress, release the pressure. Don’t let the pressure of the exam period affect your performance. Lean on a practical approach and focus on winning. Here is a step to step guide that will help you make the most out of this time.

1. Map your class notes with NCERT
Class notes play a very important role; as they are handwritten, they tend to remain in your memory. Now is the time to recall and restore all your self-made notes. Remember, whichever topic you are revising, always pull out your self-made class notes for the ultimate learning. The self-made notes have the magic to bring you in term with even the most complex concept.

While studying, keep on mapping your topic and subtopics from the NCERT and self-made notes. Underline, Highlight. Within one week, you will see that you have developed a speed.

2. Chapter wise PYQs in the sequence of Bock Strategy
Past 20 years PYQ (Previous Years’ Questions) are only necessary; there is no need to go further back in the date. Do not deviate from that; focus on these questions only, along with the continuous mapping. This way, you will start gaining more confidence in basic topics and even complex topics. Try converting your time spent in taking pressure and use that energy to increase productivity.

3. AD Revision Plan
AD stands for alternate days. It would be best if you formed a revision plan based on the alternate day strategy. If you are revising Physics, Biology (Botany) on Monday, you should revise Chemistry and Biology (Zoology), and the cycle continues.

Note: you should fix the time for revision at two hours before sleeping, and you must revise based on the AD Plan. It would be best if you planned to revise what you had studied in the week/prior week. Remember, immediate revision gives the best result—Reattempt the PYQs as a part of the revision plan.

This way, you will be using the 30 days very productively and effectively. These 30 days will boost and align your energy very immensely.

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2021-07-24 11:35:59 12. Reactivity=
C
13. Metallic character=
C< Si < Ge < Sn < Pb

14. Acidic character of the oxides=
Co2 > SiO2 > Ge02 > SnO2 > PbO2

15. Reducing nature of hydrides=
CH4 < SiH4 < GeH4 < SnH4 < PbH4

16. Thermal stability of tetrahalides=
CCl4> SiCl4> GeCl4> SnCl4 > PbCl4

17. Oxidising character of M+4 species=
GeCl4 < SnCl4 < PbCl4

18. Ease of hydrolysis of tetrahalides=
SiCl4 < GeCl4 < SnCl4 < PbCI4

19. Acidic strength of trioxides=
N203 > P2O3 > As2O3

20. Acidic strength of pentoxides=
N2O2 > P2O2> As202 > Sb2O2 > Bi̟202

21. Acidic strength of oxides of nitrogen=
N2O < NO
22. Basic nature/ bond angle/ thermal stability and dipole moment of hydrides=
NH3 > PH3 > AsH3 > SbH3 > BiH3

23. Stability of trihalides of nitrogen=
NF3 > NCl3 > NBr3

24.Lewis base strength=
NF3
25. Ease of hydrolysis of trichlorides=
NCl3 > PCI3 > AsCl3 > SbCl3 > BiCl3

26. Lewis acid strength of trihalides of P, As, and Sb=
PCl3 > ASCl3 > SbCl3

27. Lewis acid strength among phosphorus trihalides
PF3 > PCl3 > PBr3 > PI3

28. Melting and boiling point of hydrides=
H2O > H2Te > H2Se >H2S

29. Volatility of hydrides=
H2O < H2Te < H2Se < H2S

30. Reducing nature of hydrides=
H2S < H2Se < H2Te

31. Covalent character of hydrides=
H2O < H2S < H2Se < H2Te

32. The acidic character of oxides (elements in the same oxidation state)=
SO2 > SeO2 > TeO2 > PoO2
SO3 > SeO3 > TeO3

33. Acidic character of oxide of a particular element (e.g. S)=
SO < SO2 < SO3
SO2 > TeO2 > SeO2 > PoO2

34. Bond energy of halogens=
Cl2 > Br2 > F2 > I2

35. Solubility of halogen in water =
F2 > Cl2 > Br2 > I2

36. Oxidising power=
F2 > Cl2 > Br2 > I2

37. Enthalpy of hydration of X ion=
F- > Cl- > Br- >I-

38. Reactivity of halogens:=
F> Cl> Br > I

39. Ionic character of M-X bond in halides
= M-F > M-Cl > MBr > M-I

40. Reducing character of X ion:=
I- > Br- > Cl- > F-

41. Acidic strength of halogen acids=
HI > HBr > HCI > HF

42. Reducing property of hydrogen halides
= HF < HCL < HBr < HI

43. Oxidising power of oxides of chlorine
= Cl2O > ClO2 > Cl206 > Cl2O7

44. Decreasing ionic size=
02- > F- > Na+ > Mg2+

45. Increasing acidic property=
Na2O3 < MgO < ZnO< P205

46. Increasing bond length=
N2 <02 < F2 < CL2

47. Increasing size=
Ca2+ < Cl- < S2-

48. Increasing acid strength=
HClO < HClO2 < HClO3 < HClO4

49. Increasing oxidation number of iodine=
HI< I2
50. Increasing thermal stability=
HOCl < HOClO < HOClO2 < HOClO3
»»--☆

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2021-07-23 21:14:51 BORON:
•In casting of copper as a dioxidizer
•Boron rods used in automic reactor.
•Boron fiber used in bullet proof jacket,
•In composite material of aircraft
•Used in braintumer therapy.

BORAX:
•As a flux for soldring metal.
•In borex bead test
•In softning of water
•Antiseptic
•Manufacturing of enamels of glazes, tiles.
•For making optical and borosilicals SS.
•Food preservative

ALUMINIUM:
• Making house hold, untensils, frames, roof,aircrafts.
• Electric wire.
•Thermite process (In metallurgy of Cr, Mn, Fe)
•For transportin nitric acid.
•AI, Hg used as reducing agent.
•Aluminium powder + Ammonium nitrate.

LEAD [Pb]:
•In making telegraph and telephone wires
•Making bullets
•Making chamber in HSO, process.

NITROGEN:
•In the manufacturing of HNO3, NH3, CaCN2.
•Liquid nitrogen used as refrigrant.
•Inert atmosphere in metallurgy.
•Gas thermometer and electrical bulb

NH3:
• Refrigeration
•Manufacturing HNO3, NaHCO3
•Artificial Silk.
• Urea Formation
•For solvent

HNO3:
• Manufacturing of ammonium nitrateas fertilizer.
•In explosive
• For making nitroglycerine.
• Making TNT.
• Pickling against of stainless steel.
• Etching of Metal
•Oxidizer in rocket fule. Open / Comment