AIEEE 2007 - Chemistry

Answers for Questions in Chemistry (AIEEE 2007)

1. Which of the following sets of quantum numbers represents ------------

Ans. n = 3, l = 2, m = 1, s = + ½

Electrons are in the orbitals

4s, 3s, 3p and 3d

order is 3d > 4s > 3p > 3s

2. -------- hydrogen bonds is the strongest?

Ans. F – H ....F

Strongest hydrogen bond is present where the electronegativity difference is the highest

3. ------ 2Al(s) + 6HCl(aq) -----+3H₂(g)

Ans. 11.2 L H₂(g) at STP is produced for every mole HCl(aq) consumed.

6 moles of HCl liberates 3 moles of H₂, or 1 mole of HCl liberates 11.2 L of H₂ at STP

4. ----------fertilizers increases the acidity of soil?

Ans. Ammonium sulphate

Ammonium sulphate is the salt of NH₄OH (weak base) and H₂SO₄ (strong acid) and hence its regular use increases the acidity of the salt.

5. ----------- statement regarding a spontaneous process

Ans. For a spontaneous process in an isolated system, the change in entropy is positive.

6. -------- nuclear reactions will generate an isotope?

Ans. neutron particle emission

Neutron emission results in decrease in mass number by one unit, but the atomic number remains the same.

7. The equivalent conductances of two strong electrolytes --------------------- . Additional information ----------

Ans. of NaCl

= –

8. ------------------- strongest base in aqueous solution?

Ans. dimethyl amine

Due to the cumulative electron pumping effect of two methyl groups, dimethyl amine is the strongest base in liquid phase. Whereas in trimethyl amine the lone pair availability is reduced by steric hindrance.

9. --------------- oxidation of ethyl benzene by KMnO₄ is

Ans. benzoic acid

Side chain oxidation gives benzoic acid

10. The IUPAC name --------------

Ans. 3-ethyl-4, 4-dimethylheptane

3-ethyl-4,4-dimethyl heptane

11. --------------- exhibits the diamagnetic behaviour?

Ans. O₂^2-

The additional two electrons in O₂^2- enters the two half-filled antibonding molecular orbitals in O₂ and there by it becomes diamagnetic.

12. The stability of dihalides ------------------

Ans. SiX₂ << GeX₂ << SnX₂ << PbX₂

Inert pair effect becomes more effective down the group

13. --------- incorrect statement --------------

Ans. Br₂ reacts with hot and strong NaOH solution to give NaBr, NaBrO₄ and H₂O.

14. ---------- increasing order of the polarizing power --------------------

Ans. K⁺< Ca²⁺ < Mg²⁺ < Be²⁺

Higher the charge density greater is the polarising power

15. Density of 3.60 M sulphuric acid --------------- by mass

Ans. 1.22

M =

d = = 1.22 g mL^-1

16. The first and second dissociation constant -------------------

Ans. 5.0 x 10^-15

H₂ AHA^- + H⁺ Ka₁ =1 x 10^-5

HA^- A^2- + H⁺ Ka₂ = 5 x 10^-10

H₂A A^2- + 2H⁺ Ka = Ka₁ x Ka₂

= 5 x 10^-15

17. A mixture of ethyl alcohol and propyl alcohol has a vapour pressure of 290 mm at 200K ----------------vapour pressure (in mm) at the same temperature will be

Ans. 350

P = p⁰_A . x_A + p⁰_B. x_B

290 = 200 x 0.4 + p⁰_B x 0.6

P⁰_B = 350 mm

18. In conversion of lime -stone to lime, CaCO₃(s) CaO(s) + CO₂(g)------------- temperature above which conversion of lime-stone to lime will be spontaneous is

Ans. 1118 K

At equilibrium D H = TD S

(or) T = = = 1118 K

Above 1118 K, D G will be negative and hence the reaction will be spontaneous.

19. The energies of activation for forward and reverse reactions for --------------- the enthalpy change of the reaction.

Ans. 20

D H = Ea_(f) – Ea_(r) = 80 – 100 = -20 kJ mol^-1

Enthalpy change is 20 kJ mol^-1

20. The cell --------------- the relative concentration of Zn²⁺ to Cu²⁺

Ans. 10^37.3

E_cell =

When the cell is completely discharged, E_cell = 0

\ -1.1 =

by = 37.3

= 10^37.3

21. The pKa of a weak acid ------------------50% of the acid is ionized is

Ans. 9.5

pH = pKa + log

when 50% of the acid is ionised, [acid] = [salt] pH, pKa

(or) pOH = 14 – pKa = 9.5

22. ------------------- The unit of rate constant for the reaction

Ans. L mol^-1 s^-1

For B, is independent of initial concentration ie order w.r. to B is 1

Rate becames double when the concentration of A alone is doubled ie the order w.r.to A is 1

Late equation is = K[A]¹[B]¹

Overall order = 2

Unit of rate constant is (moles/L)^1-n time^-1 ie L mol^-1S^-1

23. ----------- incorrect statement

Ans. 4f and 5f orbitals are equally shielded

24. ----------- has a square planar geometry?

Ans. [PtCl₄]^2-

25. ----------- molecule expected to rotate the plane of plane-polarised light?

Ans.

Glyceraldehyde is chiral and hence is optically active.

26. Secondary structure of protein

Ans. Fixed configuration of poly peptide backbone

* Answer to this question can also be a helical backbone. But as per NCERT textbook – “The secondary structure of protein refers to the shape in which a long polypeptide chain can exist.” Therefore ‘fixed configuration of the polypeptide backbone’ is the most appropriate answer.

27. ----------- reaction will yield 2,2-dibromopropane?

Ans. CH₃ – C CH + 2HBr

CH₃C º CH + HBr ® CH₃CBr = CH₂ CH₃CBr₂CH₃

28. In the reaction CH₃CH₂NH₂ + ------ (A) + (B) --------- (A) and (B) are respectively

Ans. C₂H₅NC and 3KCl

CH₃CH₂NH₂ + CHCl₃ + 3KOH ® CH₃CH₂NC + 3KCl + 3H₂O

29. The reaction of toluene with Cl₂, ---------------------- FeCl₃

Ans. o – and p – chlorotoluene

‘CH₃’ group is an O-, P- directing group.

30. ---------- nitro group in a benzene ring

Ans. deactivates the ring towards electrophilic substitution

‘NO₂’ group deactivates the benzene ring towards electrophilic substitution, whereas it activates the ring towards nucleophilic substitution.

31. ---------------- the bond order has increased and the magnetic behaviour has changed?

Ans. NO ® NO⁺

O₂ to O₂⁺ = Bond order is increased and no change in magnetic behaviour.

N₂ to N₂⁺ = Bond order is decreased and magnetic behviour is also changed

C₂ to C₂⁺ = Bond order is decreased and magnetic behaviour is also changed

NO to NO⁺ = Bond order is increased and magnetic behaviour is also changed.

32. The actinoids exhibit more number of oxidation states -------------------------

Ans. the 5f orbitals extend further from the nucleus than the 4f orbitals

33. ------------------ The fraction of the total pressure exerted by oxygen is

Ans.

CH₄ (mol. mass = 16), O₂ ( mol. mass = 32)

n: n= 2 : 1

p= . P

34. A 5.25% solution of a substance is isotonic -------------------- molar mass of the substance will be

Ans. 210.0 g mol^-1

n_A = n_B

M_A = 210

35. Assuming that water vapour is an ideal gas, --------------------- Molar enthalpy of vapourisation of water at 1 bar and 373 K = 41 kJ mol^-1 and R = 8.3 mol^-1 K^-1) will be:

Ans. 37.904 kJ mol^-1

H₂O_(l) ® H₂O_(g)

D H = D n + D nRT

D n = 1

D n = 41 – 1 83 10^-3 3 3

= 37.904 kJ mol^-1

36. In a saturated solution of the sparingly soluble strong electrolyte AglO₃ ----------- what is the mass of AglO₃ contained in 100 ml of its saturated solution?

Ans. 2.83 x 10^-3 g

Ksp = S²

S = = 10^-4moles/L