question_answer 108)

    Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why? (a) w/w (mass percentage)             (b) V/V (volume percentage) (c) w/V (mass by volume percentage)    (d) ppm (parts per million) (e) / (mole fraction)                   (f) M (molarity) (g) m (molality)

Answer:

                      (a) w/w (mass percentage) Mass percentage of a component of a solution can be expressed as Thus, the percentage by mass means the mass of the solute in grams present in l00g of the solution. (b) V/V (volume percentage) is defined as Thus, volume percentage means the volume of the liquid solute in cm3 present in 100cm3 of the solution.                                                            (c) w/V (mass by volume percentage) mass of solute dissolved in 100 mL of solution,        (d) ppm (parts per million) This parametre is used to express the concentration of very       dilute solution.                                                                                                                                          (e)(mole fraction) Mole fraction is an unitless quantity used to determine extent of an particular component present in total solution.  (f) M (molarity) Number of moles of solute dissolved in per litre of solution is known as molarity.             (g) m (Molality) Molality of any solution can be defined as number of moles of solute dissolved in per kg of solvent.