Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

A 600 W mercury lamp emits monochromatic radiation of wavelength 331.3 nm. How many photons are emitted from the lamp per second? (h = 6.626x 10-34 J-s; velocity of light = 3x108 ms-1)

  • 1 x 1019

  • 1 x 1020

  • 1 x 1021

  • 1 x 1023


C.

1 x 1021

Given, power = 600 W

λ = 331.3 nm = 331.3 × 10-9 m Power = energytime = nhvt = nhcλt or  n = power × λthc          = 600 × 331.3 × 10-9 × 16.626 x 10-34 × 3 × 108 = 1 × 1021


12.

The number of electrons, neutrons and protons in a species are equal to 10, 8 and 8 respectively. The proper symbol of the species is

  • O816

  • O818

  • Ne1018

  • O2-816


D.

O2-816

From the given data, the atomic number, Z or number of protons of the species is 8. Number of neutrons is also 8, hence atomic mass is 16. Since, the number of electrons are two more than the number ofprotons, hence it is a bi-negative species. Thus, the species is O2-816


13.

The metal that produces red-violet colour in the non-luminous flame is

  • Ba

  • Ag

  • Rb

  • Pb


C.

Rb

Alkali metals and their salts impart a characteristic colour to flame. The reason for flame colouration is that the energy ofthe flame causes an excitation of the outermost electrons which when return to their original position, give out the energy so absorbed in the visible region. Thus, Rb gives red-violet colour to the flame.


14.

According to the first law of thermodynamics which of the following quantities represents the change in a state function?

  • qrev

  • qrev - Wrev

  • qrevWrev

  • qrev + Wrev


D.

qrev + Wrev

According to first law of thermodynamics, qrev + Wrev represents the change in a state function.

E = qrev + Wrev

E is a state function.


15.

Which will liberate bromine from a solution of potassium bromide?

  • I2

  • Cl2

  • SO2

  • HI


B.

Cl2

Since, E° of Cl2 is higher than that of Br2 therefore Cl, has a higher tendency to accept electrons than Br-. Conversely, Br- ion has a higher tendency to lose electrons than Cl- ion. Therefore, the following reaction will occur 

         KBr   K+ + Br-

2Br- + Cl2   2Cl- + Br2

Thus, Br- ions are oxidised to Br2 by Cl2, which itself is reduced to Cl- ions.


16.

Which of the following fluorides does not exist?

  • NF5

  • PF5

  • AsF5

  • SbF5


A.

NF5

P, As and Sb form pentahalides of the general formula EX5 (where, E = P, As and Sb) due to the presence of vacant d-orbitals in their respective valence shell. N does not form pentahalides due to the absence of d-orbitals in its valence shell. 


17.

56 g of nitrogen and 96 g of oxygen are mixed isothermally and at a total pressure of 10 atrn. The partial pressures of oxygen and nitrogen (in atm) are respectively

  • 4, 6

  • 5, 5

  • 2, 8

  • 6, 4


D.

6, 4

According to Dalton's law

psolute = xsolute x p

Given, mass of N2 = 56 gm

 Moles of N2(nN2) = 5628 = 2 mol

Mass of O2 = 96 gm

 Moles of O2 (nO2) = 9632 = 3 mol

xN2 = 22 + 3 = 0.4xO2 = 32 + 3 = 0.6

pN2 = xN2 × p = 0.4 × 10 = 4 atm      pO2 = xO2 × p = 0.6 ×10 = 6 atm


18.

Argon is used

  • in filling airships

  • to obtain low temperature

  • in high temperature welding

  • in radiotherapy for treatment of cancer


C.

in high temperature welding

Argon is used in high temperature welding and other operations which require a non-oxidising atmosphere and the absence of nitrogen.


19.

The expression for the solubility product of Ag2CO3 will be

  • Ksp = s2

  • Ksp = 4s3

  • Ksp = 27s4

  • Ksp = s


B.

Ksp = 4s3

Ag2CO3(s)  2Ag+2s + CO32-s

Ksp = [Ag+]2CO32-] = (2s)2.s

 Ksp = 4s3


20.

Red lead is

  • PbO

  • PbO2

  • Pb3O4

  • Pb2O3


C.

Pb3O4

Red lead Pb3O4 is a red powder, which is insoluble in water.