Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

MnO42- (1 mole) in neutral aqueous medium is disproportionated to

  • 2/3 mole of MnO4- and 1/3 mole of MnO2

  • 1/3 mole of MnO4- 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


A.

2/3 mole of MnO4- and 1/3 mole of MnO2

MnO42-(1 mole) in neutral aqueous medium is disproportionated to2/3 mole of MnO4- and 1/3 mole of MnO2.

3MnO42-+ 2H2O→ MnO2 (s) + 2MnO4-+ 4OH-

For one mole-

MnO42-+23H2O →13MnO2(s) +23MnO4-+43OH-


2.

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

  • CaO(s) + CO2(g)  CaCO3(s)

  • NaCl(aq) NaCl(s)

  • NaNO3(s)  Na+(aq) + NO3-(aq)

  • N2(g) + 3H2(g)  2NH3(g)


C.

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.


3.

Among the following the weakest base is

  • C6H5CH2NH2

  • C6H5CH2NHCH3

  • O2NCH2NH2

  • CH3NHCHO


D.

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.


4.

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


B.

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


5.

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


D.

-602 kJ/mol

Heat of decomposition,E = msT = 1× 1.23× 6.12 = 7.5276 kJ

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


6.

The ion which is not tetrahedral in shape is

  • BF4-

  • NH4+

  • Cu(NH3)42+

  • NiCl42-


C.

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.


7.

Intermolecular hydrogen bonding is strongest in

  • methylamine

  • phenol

  • formaldehyde

  • methanol


D.

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.


8.

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

  • Toluene

  • Benzene

  • n-Pentane

  • 2,2-Dimethylpropane


A.

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


9.

The paramagnetic species is

  • KO2

  • SiO2

  • TiO2

  • BaO2


A.

KO2

KO2 is a superoxide of potassium containing superoxide ion, O2- 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.


10.

Among the following the strongest acid is

  • CH3COOH

  • C6H5COOH

  • m-CH3OC6H4COOH

  • p-CH3OC6H4COOH


C.

m-CH3OC6H4COOH

Among all the given options, strongest acid ism-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).