# Thread: Help me find Molarity

1. ## Help me find Molarity

the molality of a solution LiF is .866m.

if its density is 1.10g/mL, what is its molarity?

im lost. how do i get mass, so i can find the moles, and the L of the solution?

2. Hello NeedHelp!

To find the molarity given the molality and the density:

First, since you are given the molality, let's just assume that you are working with 1 kg of water as your solvent. Use this as a conversion factor to get moles of your solute:

$\displaystyle molality (m) = \frac{moles:solute}{kg:solvent}$

1) Multiply both sides by kg to get moles.

$\displaystyle m \cdot kg = mol_{LiF} = 0.866 mols$

2) Use Molar Mass of LiF to get grams

$\displaystyle 0.866 mol \cdot \frac{25.99g}{1 mol} = 22.43 g$

3) g solute + g solvent = grams solution

$\displaystyle 1000g + 22.43g = 1022.43 g$

4) Find liters

$\displaystyle 1022.43 \cdot \frac{1 mL}{1.10g} \cdot \frac{1 L}{1000 mL} = .93 L$

$\displaystyle M = \frac{mol_{LiF}}{L_{soln}} = \frac{.866 mol}{.93 L} = .932 M$