A radioactive substance disintegrate its 90% in 100 days. How muc

Subject

Chemistry

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

A radioactive substance disintegrate its 90% in 100 days. How much time it will take to disintegrate its 99.9% ?

  • 100 days

  • 200 days

  • 300 days

  • 400 days


C.

300 days

All radioactive changes follow first order kinetics.

 For the 90% completion of the reaction,

k = 2.303100 log 100100 - 90

   = 2.303100 log 10010

   = 2.303100              ...(i)

For 99.9% completion of the reaction,

k = 2.303t log 100100 - 99.9

   = 2.303t log 103    ...(ii)

On putting the value of k from equation (i), we get

2.303100 = 2.303t × 3 log 10

t = 3 × 100 day = 300 day


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2.

Which of the following has magnesium?

  • Haemoglobin

  • Chlorophyll

  • Vitamin B12

  • Haemocyanin


3.

Pure nitrogen gas is obtained from

  • NH3 + NaNO2

  • NH4Cl + NaNO2

  • N2O + Cu

  • (NH4)2Cr2O7


4.

The Modern Periodic Table is based on the properties of elements as a function of

  • atomic number

  • atomic mass

  • electronegatvity

  • electron affinity


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5.

The pH of 0.05 M solution of a strong dibasic acid is

  • 0.0

  • 1.0

  • 0.2

  • 0.5


6.

Which of the following represents the first law of thermodynamics?

  • U = q + W

  • U = p . V

  • U = H + P.V

  • H = q + W


7.

What number of subshells are possible in n = 3 energy level?

  • 7

  • 8

  • 9

  • 6


8.

For the equilibrium reaction,

2SO2 (g) + O2 (g)  2SO3 (g) + H

the increase in temperature

  • favours the formation of SO3

  • favours the decomposition of SO3

  • does not affect the equilibrium

  • stops the reaction


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9.

What is the electronic configuration of O2- ion?

  • 1s2, 2s2, 2p5, 3s1

  • 1s2, 2s2, 2p4, 3s2

  • 1s2, 2s2, 2p6

  • 1s2, 2s2, 2p4


10.

An organic compound containing C, H and N gives the following on analysis : C = 40%, H = 13.33% and N = 46.67%. What would be its empirical formula?

  • C2H7N

  • C2H7N2

  • CH4N

  • CH3N


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