EXPERIMENT 3 FREEZING POINT DEPRESSION AND VAN'T HOFF FACTOR OF SALINE SOLUTIONS PURPOSE To determine the van't Hoff factor (i) for saturated and unsaturated solutions of sodium chloride using the freezing points PRE-LAB Find the solubility of sodium chloride in water (at 0°C if possible). Be sure to record your reference. DISCUSSION When a solute is dissolved in a solvent, the freezing point is lowered in proportion to the total number of moles of solute particles present. This property, the freezing point depression, is a colligative property; that is, it depends on the ratio of solute particles to solvent particles and not on the identity of the particles (molecules, ions, or atoms). The equation that shows this relationship is AT = Kfx m (1) where AT is the freezing point depression, K, is the molal freezing point depression constant for a particular solvent, and m is the molality of the solution (in mol solute/kg solvent). When an ionic compound dissolves in water, it separates into ions. The van't Hoff factor, i, indicates the extent to which the solute separates into ions. For example, assuming that sodium chloride separates completely into ions which act independently of each other, the expected (or ideal) value of i would be 2 since there are two ions per formula unit of NaCl. However, solutions approach ideality only at very low concentrations. To account for this deviation, we use the formula AT ix Kfx m where i x m gives the total molal concentration of particles in solution. In this experiment, you will calculate the value of i for two different sodium chloride solutions and compare them to the ideal/expected value. MATERIALS Coarse salt (rock salt or kosher salt) Ice (2) EQUIPMENT 600 mL beaker Thermometer: either a glass thermometer OR a Vernier unit and thermal sensor Stirring rod
EXPERIMENT 3 FREEZING POINT DEPRESSION AND VAN'T HOFF FACTOR OF SALINE SOLUTIONS PURPOSE To determine the van't Hoff factor (i) for saturated and unsaturated solutions of sodium chloride using the freezing points PRE-LAB Find the solubility of sodium chloride in water (at 0°C if possible). Be sure to record your reference. DISCUSSION When a solute is dissolved in a solvent, the freezing point is lowered in proportion to the total number of moles of solute particles present. This property, the freezing point depression, is a colligative property; that is, it depends on the ratio of solute particles to solvent particles and not on the identity of the particles (molecules, ions, or atoms). The equation that shows this relationship is AT = Kfx m (1) where AT is the freezing point depression, K, is the molal freezing point depression constant for a particular solvent, and m is the molality of the solution (in mol solute/kg solvent). When an ionic compound dissolves in water, it separates into ions. The van't Hoff factor, i, indicates the extent to which the solute separates into ions. For example, assuming that sodium chloride separates completely into ions which act independently of each other, the expected (or ideal) value of i would be 2 since there are two ions per formula unit of NaCl. However, solutions approach ideality only at very low concentrations. To account for this deviation, we use the formula AT ix Kfx m where i x m gives the total molal concentration of particles in solution. In this experiment, you will calculate the value of i for two different sodium chloride solutions and compare them to the ideal/expected value. MATERIALS Coarse salt (rock salt or kosher salt) Ice (2) EQUIPMENT 600 mL beaker Thermometer: either a glass thermometer OR a Vernier unit and thermal sensor Stirring rod
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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With the image attached please write 3 paragraphs
1st paragraph: objective stated clearly
2nd paragraph: complete condense method describe
3rd paragraph: analysis explained
Please write it neatly, clear and organized
Please please please answer everything it's very important please answer fast
Transcribed Image Text:EXPERIMENT 3
FREEZING POINT DEPRESSION AND VAN'T HOFF FACTOR OF
SALINE SOLUTIONS
PURPOSE
To determine the van't Hoff factor (i) for saturated and unsaturated solutions of sodium
chloride using the freezing points
PRE-LAB
Find the solubility of sodium chloride in water (at 0°C if possible). Be sure to record your
reference.
DISCUSSION
When a solute is dissolved in a solvent, the freezing point is lowered in proportion to the total
number of moles of solute particles present. This property, the freezing point depression, is a
colligative property; that is, it depends on the ratio of solute particles to solvent particles and
not on the identity of the particles (molecules, ions, or atoms). The equation that shows this
relationship is
AT = Kfx m
(1)
where AT is the freezing point depression, Kf is the molal freezing point depression constant
for a particular solvent, and m is the molality of the solution (in mol solute/kg solvent).
When an ionic compound dissolves in water, it separates into ions. The van't Hoff factor, i,
indicates the extent to which the solute separates into ions. For example, assuming that
sodium chloride separates completely into ions which act independently of each other, the
expected (or ideal) value of i would be 2 since there are two ions per formula unit of NaCl.
However, solutions approach ideality only at very low concentrations. To account for this
deviation, we use the formula
AT=ix Kfx m
(2)
where i x m gives the total molal concentration of particles in solution. In this experiment, you
will calculate the value of i for two different sodium chloride solutions and compare them to
the ideal/expected value.
MATERIALS
Coarse salt (rock salt or kosher salt)
Ice
EQUIPMENT
600 mL beaker
Thermometer: either a glass thermometer
OR a Vernier unit and thermal sensor
Stirring rod
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