Question

Hello, I need help with Chemistry (AP Edition) (9th Edition) Chapter 3 1MCRQ

Answer 1

Hi,

Hope you are doing well.

QUESTION Chemistry (AP Edition,9th Edition), Chapter 3, 1MCRQ:

When a sample of an unknown element is vaporized and injected into a mass spectrometer, the results shown below are obtained. Use these data to estimate the average atomic mass of this element.

Refer the diagram(mass spectrum) in your textbook.

(A) 117 amu.

(B) between 117 and 118 amu.

(C) between 118 and 119 amu.

(D) between 119 and 120 amu.

SOLUTION:

We know that the height of the peak in a mass spectrum is directly proportional to the proportion of that element's isotope present in nature.

You can see that the 3 peaks first, second and third are at 120 amu, 118 amu and at 116 amu respectively.

Hence the average atomic mass of this element will be between 118 and 119 amu.

So the correct option is OPTION (C) between 118 and 119 amu.