Question

Element Z has 2 natural isotopes. One isotope has a mass of 15.0 amu and has a relative abundance of 29%. The other isotope has a mass of 16.0 amu and has a relative abundance of 71%. Calculate the average atomic mass for this element. Express your answer in significant digits.

a) 15.4 amu
b) 15.7 amu
c) 15.0 amu
d) 16.0 amu

Answer 1

To calculate the average atomic mass for an element with two naturally occurring isotopes, multiply the mass of each isotope by its relative abundance and then add up the results. Option b.

Step-by-step explanation:

To calculate the average atomic mass for an element with two naturally occurring isotopes, you need to multiply the mass of each isotope by its relative abundance and then add up the results.

For the given element, the isotope with a mass of 15.0 amu has a relative abundance of 29% and the isotope with a mass of 16.0 amu has a relative abundance of 71%.

Using these values, the average atomic mass can be calculated as:

(15.0 amu * 0.29) + (16.0 amu * 0.71) = 4.35 amu + 11.36 amu = 15.71 amu option b.