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प्रश्न
The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes `""_8^16X" and """_8^18X` in the sample?
उत्तर
It is given that the average atomic mass of the sample of element X is 16.2 u.
Therefore,
The atomic mass of the given element X is = 16.2 u.
Let `""_8^16 X` percentage = a
Then `""_8^18X` percentage = (100 − a)
Average mass of X = `16("a"/100) + 18((100 - "a")/100)`
16.2 = `((16"a")/100) + ((1800 - 18"a")/100)`
1620 = 1800 − 2a
1800 - 1620 = 2a
180 = 2a
a = `180/2`
a = 90
Therefore `""_8^16X"` percentage = 90%
And `""_8^18X"` percentage = 100 − 90
= 10%
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