Question

convert 3.35 x 10-8 mm into nm
fill in the following table (provide answers with two digits after the decimal):
the average mass of lithium is 6.941 amu

Explanation:

Step1: Calculate the abundance of \(^{7}\text{Li}\)

The sum of abundances of all isotopes is \(100\%\). Let the abundance of \(^{7}\text{Li}\) be \(x\). Then \(x = 100\% - 7.59\%=92.41\%\)

Step2: Set up the equation for average atomic mass

The formula for average atomic mass \(M=\sum_{i}m_{i}a_{i}\), where \(m_{i}\) is the mass of isotope \(i\) and \(a_{i}\) is its abundance. Let the mass of \(^{7}\text{Li}\) be \(m\). Then \(6.941=(6.015122\times0.0759)+(m\times0.9241)\)

Step3: Solve for \(m\)

First, calculate \(6.015122\times0.0759 = 6.015122\times\frac{7.59}{100}=6.015122\times0.0759 = 0.456558\)

Then the equation becomes \(6.941=0.456558 + 0.9241m\)

Subtract \(0.456558\) from both sides: \(6.941 - 0.456558=0.9241m\)

\(6.484442 = 0.9241m\)

\(m=\frac{6.484442}{0.9241}\approx7.02\)

Answer:

For \(^{7}\text{Li}\), the mass is \(7.02\) amu and the abundance is \(92.41\%\)