Question

an organic compound contains following compositions by mass carbon =65.4% hydrogen =5.5 % oxygen =29.1% what will be the empirical formula

Answer 1

Hello!

We use the amount in grams (mass ratio) based on the composition of the elements, see: (in 100g solution)

C: 65.4% = 65.4 g 
H: 5.5% = 5.5 g
O: 29.1% = 29.1 g

Let us use the above mentioned data (in g) and values will be ​​converted to amount of substance (number of moles) by dividing by molecular mass (g / mol) each of the values, lets see:

$C: \dfrac{65.4\:\diagup\!\!\!\!\!g}{12\:\diagup\!\!\!\!\!g/mol} = 5.45\:mol$

$H: \dfrac{5.5\:\diagup\!\!\!\!\!g}{1\:\diagup\!\!\!\!\!g/mol} = 5.5\:mol$

$O: \dfrac{29.1\:\diagup\!\!\!\!\!g}{16\:\diagup\!\!\!\!\!g/mol} = 1.81875\:mol$

We note that the values ​​found above are not integers, so let's divide these values ​​by the smallest of them, so that the proportion is not changed, let's see:

$C: \dfrac{5.45}{1.81875}\to\:\:\boxed{C\approx 3}$

$H: \dfrac{5.5}{1.81875}\to\:\:\boxed{H\approx 3}$

$O: \dfrac{1.81875}{1.81875}\to\:\:\boxed{O = 1}$

Thus, the minimum or empirical formula found for the compound will be:

$\boxed{\boxed{C_3H_3O_1\:\:\:or\:\:\:C_3H_3O}}\end{array}}\qquad\checkmark$

I Hope this helps, greetings ... DexteR!