Question

What's the relative atomic mass for Chlorine if a sample passed through a mass spectrometer yields one peak with a mass value of 35a.m.u and a relative abundance of 75% - a second peak with a mass value of 37 a.m.u and a relative abundance of 25%.?

Answer 1

To calculate the relative atomic mass of chlorine, you need to consider the masses of its isotopes (chlorine-35 and chlorine-37) and their respective abundances.

First, convert the relative abundances to decimals:

• The abundance of the first peak (chlorine-35) is 75%, so it can be expressed as 0.75.
• The abundance of the second peak (chlorine-37) is 25%, so it can be expressed as 0.25.

Next, calculate the weighted average of the isotopes' masses using their abundances:

(0.75 * 35 a.m.u) + (0.25 * 37 a.m.u) = 26.25 + 9.25 = 35.5 a.m.u.

Therefore, the relative atomic mass of chlorine, based on the given information, is 35.5 atomic mass units (a.m.u).