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NEET Chemistry Solved Question Paper 2003

Multiple Choice Questions

The ion which is not tetrahedral in shape is

BF₄^-
NH₄⁺
Cu(NH₃)₄²⁺
NiCl₄^2-

Cu(NH₃)₄²⁺

Among all the given options, Cu(NH₃)₄²⁺ is not tetrahedral in shape. Its electronic configuration is 3d⁹ 4s⁰.

One electron is shifted from 3d to 4p orbital.

2.
Among the following the weakest base is

C₆H₅CH₂NH₂

C₆H₅CH₂NHCH₃

O₂NCH₂NH₂

CH₃NHCHO

CH₃NHCHO

Among all the given options, CH₃NHCHO is the weakest base. This is because carbonyl group exerts an electro withdrawal effect due to which basicity at N-atom decreases.

Which one of the following has $∆$ S° greater than zero?

CaO_(s) + CO₂_(g) $⇌$ CaCO_3(s)
NaCl_(aq) $⇌$ NaCl_(s)
NaNO₃_(s) $⇌$ Na⁺_(aq) + NO₃^-_(aq)
N_2(g)+ 3H_2(g) $⇌$ 2NH_3(g)

NaNO₃_(s) $⇌$ Na⁺_(aq) + NO₃^-_(aq)

Among the following options, option c is correct. It is because the number of product species is greater than the number of reactant species. So it leads to positive value of entropy.

MnO $_{4}^{2 -}$ (1 mole) in neutral aqueous medium is disproportionated to

2/3 mole of MnO $_{4}^{-}$ and 1/3 mole of MnO₂
1/3 mole of MnO $_{4}^{-}$ and 2/3 mole of MnO₂
1/3 mole of Mn₂O₇ and 1/3 mole of MnO₂
2/3 mole of Mn₂O₇ and 1/3 mole of MnO₂

2/3 mole of MnO $_{4}^{-}$ and 1/3 mole of MnO₂

MnO $_{4}^{2 -}$ (1 mole) in neutral aqueous medium is disproportionated to 2/3 mole of MnO $_{4}^{-}$ and 1/3 mole of MnO₂.

3MnO $_{4}^{2 -}$ + 2H₂O→ MnO₂_(s) + 2MnO $_{4}^{-}$ + 4OH^-

For one mole-

MnO $_{4}^{2 -}$ + $\frac{2}{3}$ H₂O → $\frac{1}{3}$ MnO₂ _(s) + $\frac{2}{3}$ MnO $_{4}^{-}$ + $\frac{4}{3}$ OH^-

One gram sample of NH₄NO₃ is decomposed in a bomb calorimeter. The temperature of the calorimeter increases by 6.12 K. The heat capacity of the system is 1.23 kJ/g/deg. What is the molar heat of decomposition for NH₄NO₃ ?

-7.53 kJ/mol
-398.1 kJ/mol
-16.1 kJ/mol
-602 kJ/mol

-602 kJ/mol

Heat of decomposition, $∆$ E = ms $∆$ T = 1 × 1.23 × 6.12 = 7.5276 kJ

Molar heat of decompsoition for NH₄NO₃ = 7.5276 × 80 = 602.2 kJ/mol

The paramagnetic species is

KO₂
SiO₂
TiO₂
BaO₂

KO₂

KO₂ is a superoxide of potassium containing superoxide ion, O^2- which has three electron bond. Thus, it can be represented as-

The presence of one unpaired electron in three electron bond makes this ion paramagnetic.

Among the following the strongest acid is

CH₃COOH
C₆H₅COOH
m-CH₃OC₆H₄COOH
p-CH₃OC₆H₄COOH

m-CH₃OC₆H₄COOH

Among all the given options, strongest acid is m-CH₃OC₆H₄COOH.

-OCH₃ group displays electron withdrawing acid strengthening inductive effect at the meta position but at the para position, an electron releasing acid weakening resonance effect operates (which at this position outweighs the inductive effect).

Which of the following compounds possesses the C-H bond with the lowest bond dissociation energy?

Toluene
Benzene
n-Pentane
2,2-Dimethylpropane

Toluene

Bond dissociation energy for C - H are given below in the given molecules

C₆H₅CH₃ - 85 kcal/mol

C₆H₆ - 110 kcal/mol

CH₃CH₂CH₂CH₂CH₃ - 98 kcal/mol

C(CH₃)₄- 92 kcal/mol

Which of the following are arranged in the decreasing order of dipole moment?

CH₃Cl, CH₃Br, CH₃F
CH₃Br, CH₃Cl, CH₃F
CH₃Cl, CH₃Br, CH₃F
CH₃Br, CH₃F, CH₃Cl

CH₃Br, CH₃Cl, CH₃F

Among all the given options, option b is correct.

The values of dipole moments of methyl halides:

CH₃F - 1.51 D ; CH₃Cl - 1.56 D; CH₃Br - 1.4 D; CH₃I - 1.29 D

Therefore, CH₃Cl > CH₃F > CH₃Br > CH₃I

10.

Intermolecular hydrogen bonding is strongest in

methylamine
phenol
formaldehyde
methanol

methanol

Methanol has strongest intermolecular hydrogen bonding because it has more -OH group.

---H - O(CH₃) ----H - O(CH₃) ----H - O(CH₃)

With the increase of electronegativity and decrease in size of the atom to which hydrogen is colvalently linked, the strength of the hydrogen bond increases.