The percentage of occurrence in a sample of 5Y10 and 5Y11 are 20% and 80% respectively. Find the atomic mass of the element.
The atomic mass of the element can be calculated using the formula:
(average atomic mass) = (mass of isotope 1 × abundance of isotope 1) + (mass of isotope 2 × abundance of isotope 2)
Given that the sample contains 5 atoms each of Y10 and Y11, we can calculate the masses of the isotopes as:
Mass of Y10 = 5 atoms × 10 atomic mass units (amu)
= 50 amu
Mass of Y11 = 5 atoms × 11 atomic mass units (amu)
= 55 amu
Using the given percentages of occurrence, we can calculate the abundances of each isotope as:
Abundance of Y10 = 20% = 0.2 Abundance of Y11 = 80% = 0.8
Substituting these values in the formula, we get:
(average atomic mass) = (10 amu × 0.2) + (11 amu × 0.8)
= 2 amu + 8.8 amu
= 10.8 amu
Therefore, the atomic mass of the element is approximately 10.8 atomic mass units.