Question

The half-life of 226 ra is 1602 y. Calculate the activity of 0.1g of racl2 in which all the radium is in the form of 226 ra. Taken atomic weight of ra to be 226 g mol-1 and that of cl to be 35.5 g mol-1 .

Answer 1

Answer:

Explanation:

Given:

Half-life of radium, T1/2 = 1602 years

Atomic weight of radium = 226 g/mole

Atomic weight of chlorine = 35.5 g/mole

Now,

1 mole of RaCl2 = 226 + 71 = 297 g

297 g = 1 mole of RaCl2

0.1 g = 1297×0.1 mole of RaCl21297×0.1 mole of RaCl2

Total number of atoms in 0.1 g of RaCl2, N =0.1×6.023×1023297 = 0.02027×1022=0.1×6.023×1023297 = 0.02027×1022

∴ No of atoms, N = 0.02027 ×× 1022

 Disintegration constant, λ=0.693T12/                                             =0.6931602×365×24×3600                                             =1.371×10−11Disintegration constant, λ=0.693T12                                             =0.6931602×365×24×3600                                             =1.371×10-11

Activity of radioactive sample, A = λNλN

                                                     = 1.371×10−11×2.027×1020 1.371×10-11×2.027×1020  

                                                     = 2.8×109 disintegrations/second