The total number of neutrons in 7 mg of  14C, is:24.088×10z neutrons . The value of z is nearly

One atom of 614C has 14−6 i.e. 8 neutrons.  ∴7mg of 614C=7×10−3g14gmol−1=0.5×10−3mol =0.5×10−3mol×6.022×1023 atom mol−1 =3.011×1020 atoms   Thus, total neutrons in 7mg014C=8×3.011×1020 neutron  =24.088×1020 neutrons