Question

Use the information for the isotopes of element X to calculate the average atomic mass of X, and identify the element.
Isotope Abundance Mass (amu)
107X 51.85% 106.90509
109X 48.15% 108.90470
Help is much appreciated, a bit confused? Could you calculate and explain how? Thank much.

Answer 1

weighted average

(mass 1 x abundance of 1)+ (mass 2 x abundance of 2)= sum of both masses

Answer 2

Now that I have the sum of both masses what do i do?

Answer 3

sorry where i wrote sum of both masses, i mean weighed sum of masses, meaning average atomic mass

Answer 4

Okay so I have the sum of both masses, how do I proceed from here? I'm still confused haha.

Answer 5

(mass 1 x abundance of 1)+ (mass 2 x abundance of 2)= average atomic mass

Answer 6

You don't just add the masses

Answer 7

Yes so I have the average atomic mass, but how does this help me find the element? Is the average atomic mass the mass of the element?

Answer 8

Average atomic mass is the same as molar mass, so use a periodic table

Answer 9

106.9 *51.85 + 108.9*48.15 = 12887.3475
Okay so I have this, what did I do wrong? This is obviously not present on the periodic table.

Answer 10

you didn't use the percentages correctly.

51.85%= 0.5185

Answer 11

Thanks so much for your help!

Answer 12

no problem !