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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: panzer on March 14, 2010, 11:38:00 AM

Title: How to calculate relative isotopic mass?
Post by: panzer on March 14, 2010, 11:38:00 AM

First of all Hi everyone, i am a new member here.

I need some help with my A-Level chemistry.

I am studying about relative atomic and isotopic mass. I got a bit confused ??? when i read that the relative atomic mass is the mass of an element relative to the mass of carbon 12.

From what i understand is that any atom is this much smaller or bigger then a Carbon atom. When i read further it said that the relative formula mass of MgCl2 is 24.3+(35.5*2). Now i cant see anything about any comparison here with the carbon atom????

Could anyone pls give me some simple example to understand to concept of relative atomic mass and the Carbon stuff?

I am sorry, i am not really good in explaining. :-[ I tried my best.
I really appreciate all your help.  ;)
Thank You :)

Title: Re: How to calculate relative isotopic mass?
Post by: JGK on March 15, 2010, 04:06:10 PM

http://en.wikipedia.org/wiki/Atomic_mass (http://en.wikipedia.org/wiki/Atomic_mass) gies definintions of Relative Atomic and Isotopic Mass fairly clearly.

Title: Re: How to calculate relative isotopic mass?
Post by: cliverlong on March 15, 2010, 07:01:29 PM

In the reference given by JGK, the term "molar mass" is used in place of "formula mass".

i.e.

One can compute the molar / formula mass of a compound by adding the relative atomic masses of the elements given in the chemical formula.

Clive

Title: Re: How to calculate relative isotopic mass?
Post by: Mitch on March 16, 2010, 06:18:54 AM

Well, Magnesium is 24.3 times the mass of (1/12) of Carbon. Just the funky nature of atomic mass units.