Atoms And Nuclei Question 393

Question: The luminous dials watches are usually made by mixing a zinc sulphide phosphor with an α - particle emitter. The mass of radium (mass number 226, half-life 1620 years) that is needed to produce an average of 10 α -particles per second for this purpose is

Options:

A) 2.77mg

B) 2.77g

C) 2.77×1023g

D) 2.77×1013kg

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Answer:

Correct Answer: D

Solution:

  • |d/Ndt|=λN

Number of radius nuclei in mg=NAm226

Decay constant, λ=0.693t1/2=0.6931620×3.16×107

|dNdt|=10=6.02×1023m226×0.6931620×3.16×107
m=10×226×162×3.16×1076.02×1023×0.693 =2.77×1010g=2.77×1013kg



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