Determine the number of neutrons and their mass, present in 7 mg of `""_(6)^(14)C`. Assume that the mass of 1 neutron=mass of 1 H-atom.

Explanation

No. of neutrons present in a `""_(6)^(14)C`- atom=(14-6)=8
Number of atoms in 1 gram-atom or 14g of carbon containing only `""_(6)^(14)C` isotope=`6.022xx10^(23)`
`therefore`In 7 mg of 0.007g of carbon, number of atoms
`=(6.022xx10^(23)xx0.007)/(14)`
`therefore`In 7 mg of carbon, number of neutrons
`=(6.022xx10^(23)xx0.007xx8)/(14)=24.088xx10^(20)`
Again, mass of `6.022xx10^(23)` atoms of hydrogen=1.008g
`therefore`Mass of 1 atom of hydrogen`=(1.008)/(6.022xx10^(23))g`
=mass of 1 neutron [according to the given condition]
`=(1.008xx24.088xx10^(20))/(6.022xx10^(23))=4.032xx10^(-3)g`.