00:01
Here, mass of the mass of the na, that means sodium 22 atom or you can say isotope, ok, isotope is given as how much? 5 milligram, that means 5 into 10 to the power minus 3 gram, ok.
00:26
So, number of moles equal to what you can write? 5 into 10 to the power minus 3 gram by molar weight or molar mass you can say 23 gram per mole, that is equal to i am getting as 2 .174 into 10 to the power minus 4 mole, ok.
00:53
So, we know that in 1 mole, ok, avogadro number of atom present, so we can say number of atom present is 6 .023 into 10 to the power 23, ok.
01:23
So, in 2 .174 into 10 to the power minus 4 mole, number of atoms present is equal to what you can write? you can write as 2 .174 into 10 to the power minus 4 into 6 .023 into 10 to the power 23.
01:49
So, i am getting the value as 1 .309 into 10 to the power 20, ok.
01:59
Also it is given that half life of na 22 atom is given as 2 .6 years, ok, equal to we know 0 .693 by lambda, t half equal to, ok...