Final answer:
To solve the average atomic mass and percent abundance problem for Rubidium, set up an equation using the known average atomic mass and the masses of the isotopes with their abundances represented as variables. Solve for the abundance variable to determine the specific percentages of each isotope.
Step-by-step explanation:
To set up the percent abundance problem to calculate the average atomic mass of Rubidium (Rb) with its isotopes Rb-85 and Rb-87, you would use the following equation:
average atomic mass = (mass of Rb-85) x (abundance of Rb-85) + (mass of Rb-87) x (abundance of Rb-87)
Where the average atomic mass is given as 85.47. However, we do not know the exact percent abundances of Rb-85 and Rb-87, but we can represent them as x and 1 - x respectively, where x is the fraction (not percent) of Rb-85. So, our equation will look like:
85.47 = (85 x x) + (87 x (1 - x))
You would then solve for x to find the percent abundance of Rb-85 and subtract x from 1 to get the percent abundance of Rb-87. These calculations are based on the principle that the average atomic mass of an element with multiple isotopes is the weighted average of the masses of its isotopes, with the weights being the isotopes' abundances.