Question

How many molecules of hexane are contained in $25mL$ of hexane? The density of hexane at room temperature is $0.6548g/mol$

Answer 1

Hint : To correctly tell the answer of the question, we should know that isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. By Rearranging the density formula to solve for mass of hexane in grams, along with then dividing by molar mass of hexane to convert to moles of hexane. Then multiply by Avogadro's number.

Complete Step By Step Answer:
We should know that Hexane is a straight-chain alkane with six carbon atoms and has the molecular formula ${{C}_{6}}{{H}_{14}}.$ We should also know that isomers have the same molecular formula, but have a different arrangement of the atoms in space. We should know that in structural isomerism, the atoms are arranged in a completely different order.
Here we have given inappropriate unit for density, i.e. the correct unit is $g/mL$ and not $g/mol$
Now that we know the $m=dv$
$m=(0.6548g/mL)(25mL)=16.37g$
Now that we get the value of $m$ and we know that hexane formula is ${{C}_{6}}{{H}_{14}}$ with molar mass of around $86.185g/mol$
Thus we can say that mol of hexane is $\dfrac{16.37g}{86.18g/mol}=0.19mol$ of hexane
We can conclude that molecules of hexane are $=(0.19mol)(6.023molecules/mol)$
On further simplifying we get $\Rightarrow 1.44\times {{10}^{23}}$ molecules.

Note :
We use hexanes in industries for formation of glues for shoes, leather products. We use hexane to extract oils from seeds, for cleansing and degreasing a variety of items, and in textile manufacturing. We should know that hexanes are chiefly obtained by refining crude oil. It is important to note that like most alkanes, hexane characteristically exhibits low reactivity and are suitable solvents for reactive compounds.