Question

Calculate the % of carbon present in ethyl alcohol with a molecular formula ${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{OH}}$ .

Answer 1

Percentage of carbon in means that we have to find the mass percentage of carbon in ethyl alcohol. We have to use the formula of percentage here and then find the mass percentage.

Complete step by step answer:
As we know that ethyl alcohol is a chemical compound. It is a clear and colourless liquid and one of the main ingredients in alcoholic drinks like beer, whisky, etc. Moreover, it is a common ingredient in many cosmetic and beauty products.
In this given statement, we have to find the percentage of carbon present in ethyl alcohol, which can be find using the formula :-
${\text{Percentage of an element in compound = }}\dfrac{{{\text{Mass of that element in compound}}}}{{{\text{Molecular formula of the compound}}}}$…..(1)

Firstly, we have to calculate the molecular mass of the given compound which is ethyl alcohol [ ]. Molecular mass of ethyl alcohol can be calculated by adding the atomic mass of each element present in the compound.
${\text{Molecular mass of ethyl alcohol = 2}} \times {\text{ atomic mass of carbon + 5}} \times {\text{ atomic mass of hydrogen }}$
${\text{ + 1}} \times {\text{ atomic mass of oxygen}} + 1 \times {\text{ atomic mass of hydrogen}}$
Putting values in the above equation, we get
${\text{Molecular mass of ethyl alcohol = 2}} \times {\text{12 + 5}} \times 1 + 1 \times 16 + 1 \times {\text{1}}$
${\text{ = 46u}}$ ……(2)

Now, we have to find the mass of carbon in ethyl alcohol. This can be found by multiplying the carbon atoms with their atomic masses i.e.
${\text{Mass of carbon = 2 }} \times {\text{atomic mass of carbon}}$
${\text{or Mass of carbon = 2 }} \times {\text{12 = 24 u}}$……(3)

Now put values from equation $(2)$ and $(3)$ in equation $(1)$, we get
${\text{Percentage of Carbon in }}{{\text{C}}_2}{{\text{H}}_5}{\text{OH = }}\dfrac{{24}}{{46}} \times 100 = 52.17\%$
Hence, the required answer is $52.17\%$

Note:
Percentage of hydrogen and oxygen can also be find in ${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{OH}}$ by the above method. Remember that the sum of the percentages of all the elements in the compound is always equal to $100\%$ . It means that the percentage of hydrogen, oxygen and carbon in ${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{OH}}$ should give the sum as $100\%$ .