Question

1. calculate the average atomic mass of lithium, which occurs as two isotopes that have the following atomic masses and abundances in nature: li - 6.017, 7.30% and li - 7.018, 92.70%.

Explanation:

Step1: Convert abundances to decimals

The abundance of \(Li - 6.017\) is \(7.30\%=0.073\), and the abundance of \(Li - 7.018\) is \(92.70\% = 0.927\)

Step2: Use the formula for average atomic mass

The formula for average atomic mass \(M=\sum_{i}m_{i}x_{i}\), where \(m_{i}\) is the atomic mass of the isotope and \(x_{i}\) is its abundance.
So, \(M=(6.017\times0.073)+(7.018\times0.927)\)
First, calculate \(6.017\times0.073 = 6.017\times(73\times10^{- 3})=(6\times73 + 0.017\times73)\times10^{-3}=(438+1.241)\times10^{-3}=439.241\times10^{-3}=0.439241\)
Second, calculate \(7.018\times0.927=(7 + 0.018)\times0.927=7\times0.927+0.018\times0.927=6.489+0.016686 = 6.505686\)
Then, \(M=0.439241+6.505686=6.944927\approx6.94\)

Answer:

\(6.94\)