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Solutions are homogenousmixtures or chemicalsystems comprised of asolute and a solvent.

The solute is the

component beingdissolved while the solventis the part in which thesolute is being dissolved.

Solutions may exist indifferent phases, either assolid, aqueous or gaseousphase.

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The solubility of solutions may be affected bydifferent factors such as pressure, temperatureand the nature of its solute and solvent.

There are properties of solutions, which areindependent on the nature of the solute, but

dependent on the amount or quantity of thesolute present. These are what we call ascolligative properties.

The Van t Hoff factor on the other hand is thenumber of ions that a compound will dissociateinto when completely ionized. For non-electrolyticsolutions, the Van t Hoff factor is always 1

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OBJECTIVES:

to determine the factors affecting solubilityand how these factors affect solubility(temperature, nature and pressure)

to calculate the boiling point elevation andfreezing point depression of solutions

to compare the colligative properties ofsolutions containing electrolyte and non-electrolyte solutes

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METHODOLOGY

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FACTORS AFFECTING SOLUBILITY

+ 10 drops water

+ 10 ethyl alcohol

+ 10 hexane

1.Nature of solute and solventsAdd to test tubes A, B, C respectively a pinch of copper sulfate (CuSO4) crystals a pinch of sucrose (C12H22O11) a drop of cooking oil a crystal of iodine (I2)Determine if the solvent can dissolve thesolute

2. Pressure

Open a bottle of carbonated soft drink toobserve the effect of pressure.

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a) 5-ml carbonatedsoftdrink was measuredinto a 10-ml test tube.Then it was heated

b) 5-ml water + pinch of saltinto a 10-ml test tube. Then it

was heated3. Temperature

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A drop of 0.1 M ammonium hydroxide wasadded into both test tubes.(with 2mL

water) Then two drops of phenolphthaleinwas also added to both test tubes

Heat was applied to the other test tubewhile the other has none.

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COLLIGATIVE PROPERTIESBOILING POINT ELEVATION

5 drops of the liquid was placed in aculture tube.

The ff. liquids will be used in different setups distilled water

1 molal sucrose 0.5 molal NaCl.

The average of the two temperatures was computedthis is the boiling point of the liquid.

The oil bath is then reheated and the temperature atwhich the first bubbles came out of the capillary is

also recorded.

The flame was removed to allow the bath to coolslowly. The temperature at which the bubblingstopped and the liquid just starts to enter the

capillary was noted and recorded.

The oil bath was heated with an alcohol lamp until arapid and continuous steam of bubbles came out of

the capillary tube.

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COLLIGATIVE PROPERTIESFREEZING POINT DEPRESSION

3-ml of a 3 molal urea solution wasplaced in a 20-ml test tube

The test tube was covered with a cork

stopper fitted with a thermometer wherethe bulb is immersed in the solution.

The test tube is then placed in an icebath containing crushed ice andheaping spatulafuls of rock salt.

The temperature was recorded every 30seconds until the reading on thethermometer became constant.

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OSMOSIS

Two raisins of the same size wereselected for this experiment.

One raisin was placed in a test tubecontaining 5-ml of water while the otherraisin was placed in a test tube containing

5-ml of 3% sugar solution.

The test tubes were observed andcompared

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CuSO4C12H22O11

OilI2

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I. NATURE OF SOLUTES AND SOLVENTS

Solvent/Solute CuSO4 C12H22O11 Oil I2 SolvenPolarity

H2O Dissolved Dissolved Didn t dissolve Didn t dissolve P

C2H5OH PartiallyDissolved

PartiallyDissolved

PartiallyDissolved

PartiallyDissolved

Partially orPartial

Non-polHexaneDidn t dissolve Didn t dissolve Dissolved Dissolv

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What did you observe upon opening abottle of carbonated softdrink?

There is effervesce or bubble formationwhen the bottle was opened. Fizzingsound was also heard..

Effect of Pressure on Solubility

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Effect of Pressure on Solubility

Account for your observations.

Since the carbonated softdrink contains pressurized CO 2 and air, when the bottle wasopened, it made a fizzing sound and formedbubbles because the pressure inside the bottle ishigher that the pressure outside the bottle. Whenthe bottle was opened, the gas (which is

pressurized) escaped. This can be proven throughHenry s Law where the solubility of a gas in aliquid increases as the pressure of the gas over theliquid increased

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EFFECT OF TEMPERATURE ON SOLUBILITY

What is the effect of temperature on the

solubility of ammonia (NH 3) in water?

As the temperature increases, the solubility

of ammonia in water decreases. How does temperature affect the

solubility of NaCl in water?

As the temperature increases, the solubilityof NaCl in water increases. The higher the

temperature, the higher the solubility.

What conclusion can you make regardingthe solubility of a gas in liquid?

As the temperature increases, the solubilityof gas in liquid decreases. Temperature isinversely proportional to the solubility of gas

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COLLIGATIVE PROPERTIESBoiling Point Elevation

Tb = mKb

Tb change in boiling point

m molality of the soluteKb ebullioscopic constant/molal boiling point

constant

Freezing Point ElevationTf = mKf

Tf change in boiling pointm molality of the soluteKf cryoscopic constant/ molal freezing point constant

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COLLIGATIVE PROPERTIES

1 m NaCl Expt al Tb = TNaCl Twater= 109 oC 100 oC= 9 oC

0.5 m sucrose Expt al Tb = Tsucrose

Twater= 115.5 oC 100

oC= 15.5 oC

1 m sucrose Expt al Tf = Twater Turea= 0 oC (-5 oC)= 5 oC

i 1m NaCl = T b experimental

T b theoretical= 9 oC

mK b= 9 oC

(1m)(0.52 oC/m)= 17.3

i 0.5msucrose = T b experimental

Tb

theoretical= 15.5 oC

mK b= 15.5 oC

(0.5m)(0.52 oC/m)

i 3 m urea = T f experimental

Tf theoretical= 5 oCmK f

= 5 oC______

(3m)(1.86 oC/m)

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GUIDE QUESTIONS AND ANSWERS1. How does the nature of the solute affect thecolligative properties, i.e., boiling point, freezing point,and osmotic pressure of the solution?

Colligative properties are dependent upon the

concentration of the solute. Non-electrolytes don

tdissociate when they dissolve while electrolytesdissociate into ions when dissolved in solvents.However, colligative properties are independent of the

nature of the solute, and it depends only upon theconcentration of solute particles.

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2. What is the significance of the Van t Hoff factor?Account for the difference in the values of thetheoretical and the experimental Van t Hoff factor forNaCl.In physical chemistry, the Van t Hoff factor I is thenumber of moles of solute in solution per mole of solid

solute added. The Van t Hoff factor is also a correction factor inserted in the equations for the colligative properties. It accounts for the dissociation of theelectrolyte solutes into ions and thus, increasing the

solute particle concentration. The difference betweenthe theoretical and experimental Van t Hoff factorshows human errors and inaccuracy of the equipmentused.

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3. Why do green mangoes lose water and shrinkwhen pickled in brine solution?

Due to the principle of osmosis, greenmangoes loose water and shrink because it isexposed to hypertonic solution. Water moves

from the area of lower solute concentration tothe solute with higher concentration.

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4. Calculate the freezing point of a 50% aqueous solution of ethylene glycol[C

2H

4(OH)

2] using the K

f of water which is 1.86

C/modal.

Given:50% aqueous solution of C 2 H4 (OH)2Kf of water = 1.86

C/mMW [C 2 H4 (OH)2 ] = 62g/mol

50% solution = 50 g [C 2 H4 (OH)2 ] in 50 g waterMol [C 2 H4 (OH)2 ] = (50 g)(1mol/62g)

= 0.806 mol C 2 H4 (OH)250 g water = .05 kg waterm = (0.806 mol [C 2 H4 (OH)2 ])

(0.05 kg water or solvent)

= 16.12 mT

f = K fm= (1.86

C/m)(16.12 m)= 29.9832~Freezing point = 0 29.98C = - 29.98

C

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5. The boiling point of pure acetone (Kb

= 1.7

C/m) is 56.50

C. What isthe boiling point of a 0.100 m solution of a non volatile non electrolytesolute in acetone?

Given:Kb = 1.7

C/mBoiling point = 56.50

Cmolality = 0.100 mT b = Kbm= (1.7

C/m)(0.100 m)= 0.17

CElevated boiling point = 56.50

C+0.17

C= 56.670

C

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CONCLUSION

there are factors that affect solubility and colligativeproperties of solutions are affected by the solutepresent in it

A solution is a homogeneous mixture composed oftwo or more substances.

There are two components in a solution, which is thesolute and the solvent.

Solvent is the component present in greatest amountwhile the other components in the solution are calledsolute.

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The factors that affect solubility are the nature of

solutes and solvents, temperature and pressure. The nature of solute and solvent affects solubility interms of their polarity, which can be generalized as like dissolves like .

Polar solutes tend to dissolve in polar solvents whilenon polar solutes tend to be insoluble in polarsolvents. The other factor that affects solubility istemperature.

The solubility of gas decreases as the temperature

increases, while the solubility of solid solutesincreases as the temperature increases.

In pressure as a factor affecting solubility, it isdescribed in Henry s Law that as the pressureincreases, the solubility also increases.

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Colligative properties are properties of solutions that arenot affected by the nature of the solute but affected bythe amount of solute present in the solution.

Boiling point elevation is the change in boiling point ofthe solvent due to the addition of solute, described in theequation T b = iKbm.

Freezing point depression is given by the equation T f =iKf m, a decrease in the freezing point of the solvent in itspure state because of the addition of solute.

The Van t Hoff factor is the number of ions that acompound will dissociate into when completely ionized.For non electrolytes, the Van t Hoff factor is alwaysone.

Osmotic pressure is the pressure that should be appliedto a solution to prevent the inward flow of water across asemi-permeable membrane.

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RECOMMENDATION

There are human errors that occurredwhile conducting the experiment. Toavoid human errors and provide a better

result, the equipment (e.g.thermometer) should be tested first.Accuracy in results is very significant .

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REFERENCES:

Ilao, L. & Engle, H. (2008). Learning modules in General Chemistry I.University of the Philippines Manila.

Chang, R. (2007). Chemistry. McGraw Hills Publicating Company:Dubuque, IA.

N.A. (n.d). Solutions and colligative properties: Colligative properties.Retrieved fromhttp://library.thinkquest.org/C006669/data/Chem/colligative/colligative.html

ABERIN, Marvin Angelo E.

BALEROS, Dessa Anne Victoria C.

GROUP 6, TAB1

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