(Download) INJSO Olympiad Question Papers 2018

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(Download) INJSO Olympiad Question Papers 2018



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 INJSO Olympiad Question Papers 2018

Section B

Question 31 (A) PD of 1 V, gains 2 eV therefore charge of ion is -2 C

  • The number of electrons in the ion = X
  • Then the number of neutrons will be X + 25 X/ 100 = 1.25X
  • The number of electrons in the neutral atom = X-2
  • The number of protons in the neutral atom = X -2
  • Mass number = No. of Protons + No. of neutrons
  • 79 = X-2 + 1.25X
  • 2.25 X = 81
  • X = 81 / 2.25 = 36

Number of protons = 36 – 2 = 34 Hence the element is Se Symbol of Ion is Se-2

(B) A = Ca B= CaOCl2 Y= Ca(OH)2 Z= CaSO4

  •   Reactions: 2Ca + O2  2CaO
  •   CaO + H2O  Ca(OH)2
  •   Ca (OH)2 + H2SO4  CaSO4 + 2H2O
  •   Ca (OH)2 + Cl2  CaOCl2 + H2O
  •   OR 2Ca(OH)2 + 2Cl2  Ca(ClO)2 + CaCl2 + 2H2O

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