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In a periodic table, the average atomic ...

In a periodic table, the average atomic mass of magnesium is given as 24,312 u. The average value is based on their relative natural abundance on earth. The three isotopes and their masses are `" "_(12)^(24)Mg `(23.98504 u), `" "_(12)^(25)Mg` (24.98584 u) and `" "_(12)^(26)Mg `(25.98259 u). The natural abundance of `" "_(12)^(24)Mg` is 78.99% by mass. Calculate the abundances of the other two isotopes.

Text Solution

Verified by Experts

It is given that abundance of `" "_(12)^(24)Mg` (23.98504 u) is 78.99%. Let abundance of `" "_(12)^(26)Mg` (25.98259 u) be x%. Then abundance of `" "_(12)^(25)Mg` (24.98584 u) will be `[100 - (78.99 + x)]% or (21.01 - x)%`.
`therefore` Average atomic mass `24.312=(23.98504 xx 78.99 + 24.98584 (21.01 - x) + 25.98259 (x))/100 implies 2431.2 = 1894.5783 + 524.9525 + 1.0006 x implies x= (2431.2 - 1894.58 -524.95)/1.0006=11.7 %`.
Hence, the abundance of `" "_(12)^(26)Mg` is 11.70% and that of `" "_(12)^(25)Mg` is (21.01 - 11.70) =9.3%.
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In a periodic table, the averge atomic mass of magnesium is given as 24.312 u . The average value is based on their relative natural abundance on earth. The three isotopes and their masses are ._12Mg^(24) (23.98504u) , ._(12)Ng^(25) (24.98584) and ._12Mg^(26) (25.98259 u) . The natural abundance of ._12Mg^(24) is 78.99% by mass. Calculate the abundances of the other two isotopes.

Average atomic mass of magnesium is 24.31 amu. This magnesium is composed of 79 mole % of 24mg and remaining 21 mole % of 25mg and 25mg . Calculate mole % of 26mg .

Knowledge Check

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