Question

The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of

isotopes 8X

16 and 8X

18 in the sample​

Answer 1

Correct Question :-

The average atomic mass of a sample of an element X is 16.2u. What are the percentages of isotopes ¹⁶₈X and  ¹⁸₈X in the sample?  

Answer :-

Given :

• Average atomic mass of a sample element X = 16.2u.

To find :

• Percentages of isotopes ¹⁶₈X and  ¹⁸₈X

Solution :

Let the percentage of ¹⁶₈X is y%.

Then,

Percentage of ¹⁸₈X is (100-y)%.

Given that average atomic mass of sample is 16.2.Therefore,

→16×(y/100) + 18(100-y)/100 = 16.2

→16y + 18(100-y) / 100 = 16.2

→16y + 18(100-y) = 1620

→16y + 1800 - 18y = 1620

→1800 - 2y = 1620

→1800 - 1620 = 2y

→180 = 2y

→y = 180/2

→y = 90%

We have,

• Percentage of ¹⁸₈X is (100-y)%

Therefore,

Percentage of ¹⁸₈X :

→100 - y

→100 - 90

→10%

Hence,

The percentages of isotopes are 90% & 10%.

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