Question

two questions:
1)1,000 g of torch emits 4700 α particles per second, ignoring the radiation from the daughter elements. Calculate the half-life

2) Nitramide, NH2NO2 decay in alkaline solution to nitrous oxide and the water. The process is of the first order. To an acetate buffer (15 ° C) was added 50.0 mg of nitramide. After 70.0 min, 6.19 ml of gas had evolved (converted to anhydrous gas at 15 ° C and 1 atm). Calculate the half-life of nitramide during the described experimental conditions!

Answer 1

1. Torch is composed mainly of Lanthanum atomic no=57.

Activity of a radioactive material or the rate of disintegration is defined as rate of disintegration per unit time.

Where dN denotes the amount or no of material disintegrated in time dt.

By Rutherford-Sody law

Where and N denotes the number or amount of radioactive material remaining after disintegration.

Also

Where denotes the half-life of the material.

Hence we can write

    …. (1)

57gm of Lanthanum has no of atoms

1000gm of Lanthanum has atoms

Activity is given as 4700 disintegration per second.

Hence, using equation (1)

This is the half life of the torch.