Question

1. calculate the average atomic mass of lithium (li), which occurs ⁶li (abundance 7.30%) and ⁷li (abundance 92.70%).

Explanation:

Step1: Convert percentages to decimals

$7.30\% = 0.0730$, $92.70\%=0.9270$

Step2: Multiply isotope mass by abundance

The mass of $^{6}Li$ is approximately 6 amu and the mass of $^{7}Li$ is approximately 7 amu.
For $^{6}Li$: $6\times0.0730 = 0.438$
For $^{7}Li$: $7\times0.9270=6.489$

Step3: Calculate average atomic mass

$0.438 + 6.489=6.927$

Answer:

$6.927$ amu