Combined Geo-Scientist 2019 Chemistry Paper I Question Paper PDF

Section A

Q1. Answer all of the following: Complete the following reaction and balance it by ion-electron method :
5×10 = 50

(a) MnO4 + Fe2+ + H+ →

(b) Carbon-14 is radioactive and beta-emitter while carbon-12 is not radioactive. Justify.

(c) Illustrate diagonal relationship with an appropriate example.

(d) Although H3PO4 is viscous it exhibits large electrical conductivity. Why ?

(e) Fe2+ is more easily oxidized to Fe3+ while Mn2+ to Mn3+ is not. Why ?

(f) Br2 melts at 7.2°C whereas ICl melts at 272°C. Explain.

(g) The dipole moment of CO is merely 0.12 D although electronegativity difference between C and O is large. Why ?

(h) The strength of HF would increase with concentration. Explain.

(i) The electrical conductance of semiconductor increases with temperature unlike those of metals. Why?

(j) Identify the product(s) in the following reaction: B2H6 + NH3(excess) low temperature →

Section B

Q2. (Attempt any one question)

(a) Which indicator is employed in the titration of acetic acid with sodium hydroxide ? Explain with suitable neutralization curve(s).
10

(b) Calculate the equilibrium constant of the following reaction at 298 K.
Zn(s) + Cu2+ ↔ Zn2+ + Cu(s)
Given: Cu2+ + 2e → Cu E° = 0.337 V
Zn2+ + 2e → Zn E° = -0.763 V
Comment on the feasibility of the above redox reaction.
10

(c) Define Lewis acid and Lewis base. Arrange BF3, BCl3 and BBr3 in the increasing order of their acid strength.
5

(d) How the concept of radius ratio governs the coordination number of the ions in a compound ? Illustrate with suitable examples.
5

Section B

Q3.

(a) Draw the molecular structures of H3PO4, H3PO3 and H3PO2. Arrange them in accordance with their pKa values.
10

(b) What is borazine? Why it is called 'inorganic benzene'? Write down the resonance structure of borazine. Why it is more reactive than benzene?
10

(c) If a copper wire is dipped into an aqueous silver nitrate solution what will happen ?
Given : Cu2+ + 2e → Cu E° = 0.337 V
Ag+ + e → Ag E° = 0.799 V
5