Question

How can I calculate the mass percent of carbon, nitrogen and oxygen in acetamide, ${C_2}{H_5}NO$ ?

Answer 1

Acetamide is an organic compound which is also named as ethanamide having the formula of $C{H_3}CON{H_2}$ . It is the simplest amide which is derived from acetic acid. The mass percent is a way of describing components in a particular mixture or the way of expressing the concentration. The mass percent of a molecule shows the amount of each element that contributes to the total molecular mass.

Formula used: $Mass\,Percentage\, = \,\dfrac{{Mass\,of\,solute}}{{Mass\,of\,solution}}\, \times \,100\%$

Complete step-by-step answer: The Mass percent of formula is expressed in the terms of the molar mass also for the mass of each element in $1{\text{ }}mole$ of the compound.
Even we can determine the mass percentage of each element with these masses.
The first step in determining the mass percent;
Given molecules are to determine each of the molecule component atomic mass.
Since, acetamide is composed of carbon, nitrogen, hydrogen and oxygen;
We get,
Molar mass carbon = $12.0\,g/mol$
Molar mass nitrogen = $14.0\,g/mol$
Molar mass oxygen = $16.0\,g/mol$
Molar mass hydrogen = $1.00\,g/mol$
Each element has its mass contribution, it is determined by multiplying the number of atoms of a certain element with their molar mass
Carbon contributes,
$2\, \times \,12.0\,\, = \,24.0\,g/mol$
Nitrogen contributes,
$1\, \times \,14.0\,\, = \,14.0\,g/mol$
Oxygen contributes,
$1\, \times \,16.0\,\, = \,16.0\,g/mol$
Hydrogen contributes,
$5\, \times \,1.00\, = \,5.0\,g/mol$
Adding each of the element’s contribution gives us the molecule's total atomic mass;
Molar mass${C_2}{H_5}NO$;
$= 24.0 + 14.0 + 16.0 + 5.00$
$= 59.0\,g/mol$
The last step to determine is the molecule’s mass percent;
It is divided with each element's contribution by acetamide's molecular mass and to multiply the result by $100\%$ .
Mass percent of carbon;
$= \,\dfrac{{24.0}}{{59.0}}\, \times \,100\, = \,\,40.7\,\%$
Mass percent of nitrogen;
$= \,\dfrac{{14.0}}{{59.0}}\, \times \,100\, = \,\,23.7\,\%$
Mass percent of oxygen;
$= \,\dfrac{{16.0}}{{59.0}}\, \times \,100\, = \,\,27.1\,\%$
Mass percent of hydrogen;
$= \,\dfrac{{5.0}}{{59.0}}\, \times \,100\, = \,\,8.5\,\%$
Always remember to cross-check the validity of the answer, just by adding up all the percentages
$40.7 + 23.7 + 27.1 + 8.5 = 100\%$

So, acetamide is having $40.7\%$ Carbon, $23.7\%$ Nitrogen, $27.1\%$ Oxygen, and $\;8.5\%$ Hydrogen.

Note: The mass percentage can be described as the mass of solute present in a given mass of a solution. The quantity of a solute can be expressed in the form of moles or mass. For a solution, the mass percentage is defined as the grams of solute in a solution, multiplied by $100$ to get the percentage.