Question: The percentage of oxygen in a compound is \[4\% \]. Its minimum molecular mass will be __________. ...

Question

The percentage of oxygen in a compound is $4\%$ . Its minimum molecular mass will be __________.
A.100
B.400
C.200
D.32

Answer 1

Solution

Mass percentage composition is also known as a percentage by weight. In case of a solution, the mass percentage is equal to the mass of an element present in one mole of the compound divided by the molar mass of the given compound and it will be multiplied by $100\%$ . The relation between the percentage of an element in a compound and its molecular mass is given as:
$Mass\% = \dfrac{w}{M} \times 100\%$
Where:
$Mass\%$ = Mass percentage of a given element
W is Given the mass of the element
M is the Molecular mass of the given element

Complete step by step answer:
-Since we have been given the percentage of oxygen in the compound so let us consider the weight of the compound to be x grams. Since the percentage of oxygen in the compound is given and we need to give the minimum molecular mass of the compound so the given weight of oxygen should also be minimum which must be $16grams$ as minimum 1 atom of oxygen should be there in the compound.
-Now we will put these values in our formula:
$Mass\% = \dfrac{w}{M} \times 100\%$
-Here, Mass percentage of given element $= 4\%$
Given the mass of element $= 16g$
-We have to find the molecular mass of the compound.
Substituting in the above formula:
$4 = \dfrac{{16g}}{M} \times 100\%$
$\Rightarrow M = \dfrac{{16}}{4} \times 100$
$\Rightarrow M = 4 \times 100$
$\Rightarrow M = 400grams$
Hence we can conclude that the molecular mass of the compound is $400grams$ .
Option B is the correct answer.

Note:
-Mass percent composition describes the relative quantities of elements in a compound.
-The percentage composition of a compound can also be determined from the formula of a compound. From the subscripts of each element in a compound, mass of each element in one mole of a compound can be calculated. A component in a particular mixture can be described by the mass percent. The solution composition can be described as the mass of solute in a given mass of solution.