Question

Kemmi pipets 25.00 mL of pure 1-propanol (C₃H₇OH, a liquid organic alcohol) into a 100.0 mL volumetric flask. She dilutes it with water. Help her calculate the strength of her diluted solution.

Volumes: 25.00 mL volumetric pipet, 100.00 mL volumetric flask.

Molar mass of pure 1-propanol: 60.09 g/mol. Density of pure 1-propanol: 0.803 g/mL

Calculate the number of moles in exactly 25.00 mL of 1-propanol. (3 significant figures; units of mol)  [x]

Calculate the molarity of the diluted solution. (3 significant figures; units of M or mol/L)  [y]

Answer 1

V = 25 mL
density = 0.803 g/mL
mass of propanol= V* density
                                   = 25 mL*0.803 g/mL
                                   = 20.075 g
Molar mass = 60.09 g
number of moles of propanol = mass / molar mass
                                                             = 20.075/60.09
                                                             = 0.334 mol

Final volume = 100 mL = 0.1 l
final concentration = number of moles / volume
                                        = 0.334/0.1
                                        = 3.34 M
Answer: X = 0.334 mol
Y= 3.34 M