Q47P - Chemistry: Molecular Nature Of Matter And Change

Question

Gallium has two naturally occurring isotopes, ⁶⁹Ga (isotopic mass 68.9256 amu, abundance 60.11%) and ⁷¹Ga (isotopic mass 70.9247 amu, abundance 39.89%). Calculate the atomic mass of gallium.

Step-by-Step Solution

Answer

Atomic mass of gallium is the total sum of atomic mass from isotope ⁶⁹Ga and isotope ⁷¹Ga.

Step 1: Calculation of portion of atomic mass from 69 Ga

Portion of atomic mass from ⁶⁹Ga = isotopic mass x fractional abundance

                                                       = 68.9256 x 60.11/100

                                                       = 41.43 amu

Step 2: Calculation of portion of atomic mass from 71 Ga

Portion of atomic mass from ⁷¹Ga = isotopic mass x fractional abundance

                                                       = 70.9247 x 39.89/100

                                                       = 28.29 amu

Step 3: Calculation of atomic mass of gallium

Atomic mass of gallium = atomic mass from ⁶⁹Ga + atomic mass from  ⁷¹Ga

                                      = 41.43 amu + 28.29 amu 

                                      = 69.72 amu