680 g of sodium 24 was placed in a container to decay if there is now 85 g of sodium 24 left how long has the sodium been decaying

Explanation:

The time taken for the radioactivity of a specified isotope to fall to half its original value is called half life of that radioactive material.

Half life of sodium-24 is hours.

Initial amount of sodium-24 is

In hours,the quantity falls to

In another hours,the quantity falls to

In another hours,the quantity falls to

So,it takes hours for the quantity to become .

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.