Question

A patient has a cholesterol level of $232\text{mg/L}$. What is the molarity of cholesterol in this patient's blood if the molar mass of cholesterol is $386.64\text{g/mol}$?

• A. $7.2\times {10}^{-3}M$
• B. $2.5\times {10}^{-4}M$
• C. $4.5\times {10}^{-3}M$
• D. $6\times {10}^{-4}M$

Answer 1

The correct option is D $6\times {10}^{-4}M$

Mass of cholesterol in 1 L $=232\times {10}^{-3}g$
Number of moles of cholesterol $=\frac{\text{weight}}{\text{molar mass}}=\frac{232\times {10}^{-3}g}{386.64\text{g/mol}}=6\times {10}^{-4}\text{mol}$
$\text{Molarity}=\frac{\text{number of moles}}{\text{volume in L}}$
$=\frac{6\times {10}^{-4}\text{mol}}{1L}=6\times {10}^{-4}M$