# Question 25b38

May 25, 2016

$A {l}_{2} {\left(S i {O}_{3}\right)}_{3}$

#### Explanation:

We can proceed by calculating masses of elements X,Y and Z present in the molar mass of the compound ${X}_{2} {\left(Y {Z}_{3}\right)}_{3}$
using the given percentage composition of the compound.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
So mass of X present in one mole of the compound is 282.23xx19.12%g=53.96g
Since according to the formula of the comound its molecule contains 2 atoms of X ,
$\text{the molar mass of X"=53.96/2=26.98g/"mol}$
Now from periodic table it is found that X is nothing but Al.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Similarly mass of Y in molar mass of the compound is
282.23xx29.86%=84.27g.
As the molecule contains 3 atoms of Y,
$\text{molar mass of Y"=84.27/3=28.09g/"mol}$
According to periodic table it should be Si.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Now finally 9 atoms of y are present in one molecule of the comound and its mass in one mole of the compound is
282.23xx51.02%~~144g#
Hence$\text{ ""molar mass of Z"= 144/9=16g/"mol}$
Consulting periodic table we can say the element Z is Oxygen O

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So the compound will have formula $A {l}_{2} {\left(S i {O}_{3}\right)}_{3}$ which is Aluminium silicate