Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

The pH of an aqueous solution of CH3COONa of concentration C(M) is given by:

  • 7 - 1/2 pKa - 1/2 log C

  • 1/2 pKw + 1/2 pKb + 1/2 log C

  • 1/2 pKw - 1/2 pKb - 1/2 log C

  • 1/2 pKw - pKa + 1/2 log C


2.

If the equilibrium constants of the following equilibria,

SO2 + 1/2O2  SO3 and 2SO3  2SO2 + O2

are given by K1 and K2 respectively, which of the following relations is correct?

  • K2 = (1/K1)2

  • K1 = (1/K3)3

  • K2 = (1/K1)

  • K2 = (K1)2


3.

The energy of an electron in first Bohr orbit of H-atom is-13.6 eV. The possible energy value of electron in the excited state of Li2+ is:

  • - 122.4 eV

  • 30.6 eV

  • - 30.6 eV

  • 13.6 eV


4.

The amount of the heat released when 20 mL 0.5 M NaOH is mixed with 100 ml 0.1 M HCl is x kJ. The heat of neutralisation is:

  • - 100 x kJ/mol

  • - 50 x kJ/mol

  • + 100 x kJ/mol

  • + 50 x kJ/mol


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5.

Which one of the following has the lowest ionisation energy?

  • 1s2 , 2s2 , 2p6

  • 1s2 , 2s2 , 2p6 , 3s1

  • 1s2 , 2s2 , 2p5

  • 1s2 , 2s2 , 2p3


6.

2 g of metal carbonate is neutralised completely by 100 mL of 0.1 N HCI. The equivalent weight of metal carbonate is:

  • 50

  • 100

  • 150

  • 200


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7.

An electric current is passed through an aqueous solution of a mixture of alanine (isoelectric point 6.0), glutamic acid (3.2) and arginine (10.7) buffered at pH 6. What is the fate of the three acids?

  • Glutamic acid migrates to anode at pH 6. Arginine is present as a cation and migrates to the cathode. Alanine in a dipolar ion remains uniformly distributed in solution

  • Glutamic acid migrates to cathode and others remain uniformly distributed in solution

  • All three remain uniformly distributed in solution

  • All three move to cathode


A.

Glutamic acid migrates to anode at pH 6. Arginine is present as a cation and migrates to the cathode. Alanine in a dipolar ion remains uniformly distributed in solution

Amino acids exist as Zwitter ions which contain both positive and negative charge but overall electrically neutral. At their the isoelectric point, amino acids do not migrate to any electrode and remain uniformly distributed in the solution. Thus, alanine (isoelectric point 6.0) does not move to any electrode.

At a pH lower than their isoelectric point, they exist as cation and move towards the cathode. Thus, arginine (isoelectric point 10.7 exists as the cation.

At a pH higher than their isoelectric point, they exist as anion and move towards the anode. Thus, glutamic acid (isoelectric point 3.2) at pH 6.0 moves towards the anode.


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8.

The representation of the ground state electronic configuration of He by box-diagram as 

is wrong because it violates:

  • Heisenberg's uncertainty principle

  • Bohr's quantization theory of angular momenta

  • Pauli exclusion principle

  • Hund's rule


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9.

The electronic transitions from n = 2 to n = 1 will produce shortest wavelength in (where n = principal quantum state)

  • Li2+

  • He+

  • H

  • H+


10.

In the following electron-dot structure calculate the formal charge from left to right nitrogen atom; N....=N=N.... :

  • -1 , -1 , +1

  • -1 , +1 , -1

  • +1 , -1 , -1

  • +1 , -1 , +1


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