An aqueous solution of concentrated hydrobromic acid contains 48% HBr by mass. If the density of the solution is 1.5 g / mL, What is its concentration?
Answer:
\(\text { (B): } 8.9 \mathrm{~mol} / \mathrm{L}\)
Explanation:
We’re asked to find the (molar) concentration of \(\mathrm{HBr}\) in solution, given its mass percentage and density.
To do this, we’ll first assume there is \(1 \mathrm{~L}\) of solution, so the density is also written as
\(1.5 \mathrm{~g} / \mathrm{mL}=1500 \mathrm{~g} / \mathrm{L}\)We’re given that \(48 \%\) of the mass \((1500 \mathrm{~g})\) is \(\mathrm{HBr},\) so the mass of \(\mathrm{HBr}\) is
Now, we use the \(\text { molar mass }\) of \(\mathrm{HBr}(80.912 \mathrm{~g} / \mathrm{mol})\) to calculate the number of moles:
Thus, option \((B)\) is the correct answer.