# Question #5b32a

Dec 29, 2014

Molarity represents the concentration of as solution expressed in number of moles of solute per liter of solution.

$m o l a r i t y = \left(\text{moles of solute")/("liters of solution}\right)$

So, let's say you want to make a solution of sucrose (table sugar - ${C}_{12} {H}_{22} {O}_{11}$), so you add 15 g of sucrose to 500.0 mL of water.

You first determine the number of moles of solute - in this case, sucrose:

${n}_{s u c r o s e} = \left(\text{mass")/(" molar mass}\right) = \frac{15.0 g}{246 \frac{g}{m o l}} = 0.061$ moles

Therefore, your solution's molarity will be

$C = \frac{0.061 \text{moles}}{500.0 \cdot {10}^{- 3} L} = 0.12$ $\text{moles/L}$

Notice that I've converted mL to L.

As a strategy, always try to determine how much of something - number of moles - is added to what volume of solution.

You can find other examples here

http://socratic.org/questions/how-do-you-find-molar-it-s-give-three-examples?source=search