Solve the following problems III — task. Science State Board, Class 10.

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1. Calculate the % relative abundance of $B-10$ and $B-11$ , if its average atomic mass is $10.804$ $amu$ .

Answer:

Let the % of the isotope

$B-10=x$

Then, the % of the isotope

$B-11=100-x$

$\begin{array}{l} Average atomic mass = \frac{10 \times x + 11 (100 - x)}{100} \\ 10.804 = \frac{A}{100} \\ 10.804 = \frac{B}{100} \\ x = ? \end{array}$

Where,

$=$

% abundance of

$B-10=$

% abundance of

$B-11=$

2. Calculate the percentage of oxygen in $Al_2(SO_4)_3$ (atomic mass: $Al=27$ , $O=16$ , $S=32$ ).

Answer:

Given data:

Atomic masses:

$Al=27$ ,

$O=16$ ,

$S=32$

Formula:

The formula to find the percentage of an element is

$\frac{\text{X}}{\text{Y}}\times100$

Where,

$=$

Solution:

Molecular mass of

$Al_2(SO_4)_3$

$=$

% of

$O$ in

$Al_2(SO_4)_3$

$=$

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17. Solve the following problems III

Exercise condition: