Disintegration of radium takes place at an average rate of 2.24xx10^(13) alpha-particles per minute. Each alpha-particle takes up 2 electrons from the air and becomes a neutral helium atom. After 420 days, the He gas collected was 0.5xx10^(-3)L measured at 300K and 750mm of mercury pressure. From the above data, calculate Avogadro's number.

Disintegration of radium takes place at an average rate of 2.24xx10^(1

1.	Disintegration of radium takes place at an average rate of 2.24xx10^(13) alpha-particles per minute. Each alpha-particle takes up 2 electrons from the air and becomes a neutral helium atom. After 420 days, the He gas collected was 0.5xx10^(-3)L measured at 300K and 750mm of mercury pressure. From the above data, calculate Avogadro's number.
Answer» Solution :No of `alpha` -PARTICLES (or)He formed `=2.24xx10^(13) min^(-1)` `:.` No of He particles formed in `420days=2.24xx10^(13)xx420xx1440` `=1.355xx10^(19)` Also at `27^(@)C` and `750mm`, `He=0.5ml` Using `PV=nRT` `(750)/(760)xx(0.5)/(1000)=nxx0.0821xx300` `impliesn=2.0xx10^(-5)` moles `2.0xx10^(-5)` moles of `He=1.355xx10^(19)` particles of `He` `implies1` mole of He `=(1.355xx10^(19))/(2.0xx10^(-5))` `=6.775xx10^(23)` particles `:.` Avagadro.s NUMBER `=6.775xx10^(23)` particles/mol