How to figure out which substance has the highest osmotic pressure? In preparing for an exam and I'm trying to solve the following question. I'm clueless. What should I do?


  Which of the following water solutions has the highest osmotic pressure?
  
  \begin{align}
\tag1 \pu{0.1 mol/kg} &amp;~ \ce{NaCl}\\
\tag2 \pu{0.1 mol/kg} &amp;~ \ce{KF}\\
\tag3 \pu{0.1 mol/kg} &amp;~ \text{sucrose}\\
\tag4 \pu{0.1 mol/kg} &amp;~ \ce{MgCl2}
\end{align}
$\ce{MgCl2}$ has the highest osmotic pressure because it breaks up into three ions in water, as opposed to all the others, which only break up into two.