Question

Calculate the molality, molarity, and mole fraction of FeCl3 in a 29.5 mass % aqueous solution (d = 1.283 g/mL).

Answer 1

Answer:

molality FeCl3= 2.579 molal

molarity FeCl3 = 2.333 M

mol fraction FeCl3 = 0.0444

Explanation:

Step 1: Data given

Mass % = 29.5 %

Density = 1.283 g/mL

Molar mass FeCl3 = 162.2 g/mol

Step 2: Calculate mass solution

Suppose we have 1L = 1000 mL solution

Mass solution = 1.283 g/mL * 1000 mL = 1283 grams

Step 3: Calculate mass FeCl3

Mass FeCl3 = 0.295 * 1283 grams

Mass FeCl3 =  378.485 grams

Step 4: Calculate mass of water

Mass water = 1283 - 378.485 = 904.515 grams

Step 5: Calculate moles FeCl3

Moles FeCl3 = mass FeCl3 / molar mass FeCl3

Moles FeCl3 = 378.485 grams / 162.2 g/mol

Moles FeCl3 = 2.333 moles

Step 6: Calculate moles H2O

Moles H2O = 904.515 grams / 18.02 g/mol

Moles H2O = 50.195 moles

Step 7: Mol fraction FeCl3

Mol fraction FeCl3 = 2.333 / (50.195+2.333)

Mol fraction FeCl3 =   0.0444

Step 8: Calculate molality

Molality = moles FeCl3 / mass H2O

Molality = 2.333 moles / 0.904515 kg

Molality = 2.579 molal

Step 9: Calculate molarity

Molarity = moles / volume

Molarity FeCl3 = 2.333 moles / 1 L

Molarity FeCl3 = 2.333 M