Question

part a
lead consists of four naturally occurring isotopes. calculate the atomic mass of lead.
express your answer using four significant figures.
atomic mass of pb = amu

Explanation:

Step1: Convert percentages to decimals

$1.40\% = 0.0140$, $24.10\%=0.2410$, $22.10\% = 0.2210$, $52.40\%=0.5240$

Step2: Multiply mass by abundance for each isotope

For $^{204}_{82}Pb$: $204.0\times0.0140 = 2.856$
For $^{206}_{82}Pb$: $206.0\times0.2410=49.646$
For $^{207}_{82}Pb$: $207.0\times0.2210 = 45.747$
For $^{208}_{82}Pb$: $208.0\times0.5240=109.992$

Step3: Sum up the results

$2.856 + 49.646+45.747 + 109.992=208.241$

Answer:

$208.2$ amu