Question

A patient has a cholesterol level of $206\text{mg/L}$. What is the molarity of cholesterol in this patient's blood if the molar mass of cholesterol is $386.64\text{g/mol}$?

• A. $1.3\times {10}^{-4}M$
• B. $3.3\times {10}^{-4}M$
• C. $5.3\times {10}^{-4}M$
• D. $5.3\times {10}^{-3}M$

Answer 1

The correct option is C $5.3\times {10}^{-4}M$

Mass of cholesterol in 1 L $=206\times {10}^{-3}g$
Number of moles of cholesterol $=\frac{\text{weight}}{\text{molar mass}}=\frac{206\times {10}^{-3}g}{386.64\text{g/mol}}=5.3\times {10}^{-4}\text{mol}$
$\text{Molarity}=\frac{\text{number of moles}}{\text{volume in L}}$
$=\frac{5.3\times {10}^{-4}\text{mol}}{1L}=5.3\times {10}^{-4}M$