Question

an unknown element x has the following isotopes: ²⁵x (80.50% abundant, mass = 25.03 amu) and ²⁷x (19.50% abundant, mass = 26.98 amu). what is the average atomic mass of x in amu?

Explanation:

Step1: Convert percentages to decimals

$80.50\% = 0.805$, $19.50\%=0.195$

Step2: Calculate contribution of first isotope

$0.805\times25.03 = 20.14915$

Step3: Calculate contribution of second isotope

$0.195\times26.98 = 5.2611$

Step4: Find average atomic mass

$20.14915 + 5.2611=25.41025$

Answer:

$25.41$ amu