The molar mass of dimethylmercury is [200.59 + (15x2)] = 230.59
g/mol
number of molecules in the given sample =[ mass of sample/molar
mass] x Avogadro number
                                                                          Â
= [6.05x6.023x1023]/ 230.59
                                                                          Â
= 1.580x 1022