Answer to Question #195251 in General Chemistry for marisol

Question

A solution is prepared by mixing 2 g of FeCl₃ with enough water to make 50 mL of solution. Calculate the molarity of the solution.

Answer 1

First we use the molar mass (MM) of FeCl₃ [MM = (35.45 g/mol)(3) + (55.85 g/mol)(1) = 162.20 g/mol] and the mass of solid (m) given to calculate the number of moles dissolved:

• $n = \frac{m}{MM} = \frac{2\,\cancel{g}}{162.20\,\cancel{g}/mol} = 0.01233 \,mol$

The molarity of the solution (M) can be calculated with the number of moles of solute (n) and the volume of the solution (V) already given (remember that the volume has to be expressed in liters):

• $M = \frac{n}{V} = \frac{0.01233\,mol}{50\, mL} = \frac{0.01233\,mol}{0.05\, L} = 0.2466 \,mol/L$

To conclude, it is found that the molarity of FeCl₃ on the solution is 0.247 M or 0.247 mol/L