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

Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.
Advertisement

 Multiple Choice QuestionsMultiple Choice Questions

161.

In a radioactive change R -α X -β Y -β Z. R and Z.

  • isotopes

  • isobars

  • isomers

  • isotones


162.

nXemit one α and two β- particles. It is converted into

  • nXm - 4

  • n - 1Xm - 1

  • nZm - 4

  • None of these


163.

Increasing order (lowest first) for the values of e/m for electron (e), proton (p), neutron (n) and α-particles is

  • e, p, n, α

  • n, α, p, e

  • n, p, e, α

  • n, p, α, e


164.

A particle moving with a velocity 106 m/s will have de-Broglie wavelength nearly [Given, m= 6.62 × 10-27 kg, h =  6.62 × 10-34 J-s]

  • 10-9m

  • 10-13 m

  • 10-19 m

  • 1 Å


Advertisement
165.

From the given sets of quantum numbers, the one that is inconsistent with the theory is

  • n =3; l =2; m = -3; s = +12

  • n = 4; l = 3; m = 3; s = +12

  • n = 2; l = 1; m = 0; s = -12

  • n = 4; l = 3; m = 2; s = +12


166.

In the following particle

3Li6 + ? → 2He41H3

the missing particle is

  • electron

  • neutron

  • proton

  • deuteron


167.

Bohr's radius of 2nd orbit of Be3+ is equal to that of

  • 4th orbit of hydrogen

  • 2nd orbit of He+

  • 3rd orbit of Li2+

  • first orbit of hydrogen


168.

The sky looks blue due to

  • dispersion effect

  • reflection

  • transmission

  • scattering


Advertisement
Advertisement

169.

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


Advertisement
170.

The wavelength of an electron having kinetic energy equal to 4.55 × 10-25 J is (h = 6.6 × 10-34 kgm2s-1, mass of electron = 9.1 × 10-31 kg)

  • 7.25 × 10-7 nm

  • 725 nm

  • 7.25 × 10-7 m

  • 7.25 × 107 nm


Advertisement