Question

A sample of gallium contains 60% of atoms of 31Ga69 and 40% of atoms of 31Ga71. Calculate the relative atomic mass of this sample of gallium.

Answer 1

Answer:

find the average atomic mass (Ar) of an element, given the percentage rarities of its isotopes, simply multiply each isotope's Ar by its percentage that is expressed as a decimal and total the results. We can carry this out in a single line of working:

Mr(Ga)=(68.9256⋅0.60108)+(70.9247⋅0.39892)

Mr(Ga)=69.7231 to 4 decimal places

Similarly, you could input the percentages normally and then divide by 100:

Mr(Ga)=(68.9256⋅60.108)+(70.9247⋅39.892)100

Mr(Ga)=69.7231 to 4 decimal places