Illustrated Guide to Home Chemistry Experiments

Chapter 8 Laboratory: Colligative Properties of Solutions 157

oALIpToN ACTIvITIES

If you have time and the required materials, consider

performing these optional activities:

• Repeat the experiment, using prunes rather than
  celery. Record the differences, if any, in mass loss/gain
  percentages.


• It’s difficult to get quantitative results using
  vegetables. Assume that you have access to a
  commercial semipermeable membrane that
  passes water freely but blocks sucrose as well as
  an appropriate container to provide two chambers
  separated by the membrane. Design an experiment to
  provide more accurate data about osmotic pressure
  effects, including intermediate values for molality as
  the system comes to equilibrium.

FIGURE 8-3: Determining the mass of a celery sample

Celery piece/solution

% mass gain (loss) Initial massFinal massMass gain (loss)

A. Sodium chloride, 6 mol/kg________.____ g________.____ g_________.____ g

B. Sodium chloride, 3 mol/kg________.____ g________.____ g_________.____ g

C. Sodium chloride, 1.5 mol/kg________.____ g________.____ g_________.____ g

D. Sucrose, 6 mol/kg ________.____ g________.____ g_________.____ g

E. Sucrose, 3 mol/kg ________.____ g________.____ g_________.____ g

F. Sucrose, 1.5 mol/kg ________.____ g________.____ g_________.____ g

G. Water ________.____ g________.____ g_________.____ g

TABLE 8-3: Osmotic pressure—observed and calculated data

RQEWEvI UESTIOnS

q 1 : Calculate the mass gain (or loss) for each of the samples, in grams and percentage, and enter the results in Table 8-3. Note
which samples gained mass and which samples lost mass. Propose an explanation.