Solutions Ppt

Experiment 6:

SOLUBILITY-ARIENZA, Mariane Allen J.

-VELEZ, Vida Valerie V.

Introduction

A solution is a homogenous mixture of two or more pure substances

•Solute – more chemically active component; usually in lesser amount•Solvent – component of greater quantity

The amount of solute that dissolves in a fixed quantity of solvent at a given temperature, referred to as solubility, is affected by certain factors .

Introduction

Factors affecting Solubility:

Nature of Solute and Solvent

“Nature” refers to the type of substance – whether it is polar or nonpolar. The nature of substance determines the type of interparticular forces of attraction.

Introduction

Factors affecting Solubility:

Temperature

Pressure

Introduction

Colligative Properties

Colligative Properties are not influenced by the nature of solute and solvent. They are only dependent on the amount of solute in the solution.

Introduction

Colligative Properties

Boiling Point Elevation

Freezing Point Depression

Osmosis

APPARATUS NEEDED

Methodology

10-ml test tube

Glass rodThermometer

10-ml graduated cylinder

Methodology

50-ml beaker20-ml test tubes

Cork borer

Methodology

MATERIALS NEEDED

Methodology

Copper sulfate crystals Hexane Urea solution Sodium chloride O.1 N NH4OH Glycerine 3% sucrose solution

Methodology

phenolphthaleinEthyl alcohol C2H5OHSucrose crystalsI2 crystalsRock saltCooking oilSoftdrinksRaisinsIce cubes

Methodology

PART A

FACTORS AFFECTING SOLUBILITY

Methodology

MethodologyNature of Solute and Solvent

1


2


Shake each mixture vigorously and observe.

Repeat the above procedure using the following solutes in place of copper

sulfate:A pinch of sucrose

1 drop of cooking oilA crystal iodine (I2)

3

4

MethodologyPressure

Open a bottle of carbonated softdrink and observe.

MethodologyTemperature

Allow the effervescence to subside.

2

3

1A


B

3

1

2


C

31 2

PART B

Colligative Properties of Solutions

Methodology

MethodologyBoiling Point Elevation

5 drops of dist. H2O were transferred in a 6 x 50 culture tube. One end of the capillary tube was closed and the open end was first inserted in

the culture tube.

The tube was attached to a thermometer by means of a rubber ring for the liquid to be aligned with the mercury bulb and the thermometer was

immersed into the tube in an oil bath (10 mL beaker containing 5 mL mineral oil).

The bath was heated with an alcohol lamp until rapid continuous stream of bubbles came out from the capillary.

The flame was removed and the bath was allowed to cool slowly.

The bath was reheated slowly and the temperature at which the first bubbles come out of the capillary was noted.

MethodologyBoiling Point Elevation

The average of the two temperature readings were determined and recorded as

the boiling point of the liquid.

The same procedure was done to determine the boiling point of 1 molal sucrose and 1

molal NaCl.

MethodologyFreezing Point Depression

When the reading became constant, the thermometer

was read and the temperature was recorded

MethodologyOsmosis

The rate of swelling of raisins were then observed.

RESULTS (PART A)

SOLVENT/SSOLUTE

CuSO4 C12H22O11 OIL I2 SOLVENT POLARIT

Y

H20 soluble soluble immiscible insoluble polar

C2H5OH partially insoluble

partially soluble

partially immiscible

soluble partially polar

HEXANE insoluble insoluble miscible Soluble non-polar

Figure 1.

I. Nature of Solute and Solvent

GUIDE QUESTIONS: ( PART A )

1) What did you observe upon opening a bottle of carbonated softdrink?

ANSWER:

Upon opening the bottle of softdrink, a fizzing sound was produced and bubbles formed on top of the liquid and lasted for a short time.

II. Effect of Pressure on Solubility

II. Effect of Pressure on Solubility2.)Account for your observations.

ANSWER:

A carbonated drink , when opened, forms bubbles when dissolved Carbon Dioxide ( CO2) is depressured forming emulsions at the top. It makes that fizzing sound because the pressure inside the bottle escapes. The decrease in pressure decreased the solubility of CO2 in the solution forming bubbles and a fizzing sound which is called effervescence.

III. Effect of Temperature on Solubility

1) What is the effect of temperature on the solubility of ammonia (NH3) in water?

ANSWER:

The higher the temperature, the less NH3 is dissolved by water. The more NH3 is dissolved by water, the lower the temperature. (exothermic) The solute-solvent attraction is stronger than the solvent-solvent and solute-solute attraction.


2.) How does temperature affect the solubility of NaCl in water?

ANSWER:

The solubility of NaCl in water increases as the temperature increases, thus, they’re directly proportional. (endothermic) The solute-solvent attraction is weaker than the solvent-solvent and solute-solute attraction.


3.) What conclusion can you make regarding the solubilty of a gas in liquid?

ANSWER:

The solubility of a gas in a liquid decreases as the temperature increase, thus, they’re inversely proportional. An increase in the temperature increases the energy of the gas molecules, thus, decreasing the solubility.

RESULTS (PART B)

SOLUTION ______

INITIAL READING

BOILING POINT

FINAL READING

______

AVERAGE READING

FREEZING POINT

EXPT’AL Tb or Tf

EXPT’AL Van’t Hoff

Factor

Dist. H2O 157.5o C

145oC 151.25o

CXXX XXX XXX

1 m NaCl

120oC 141oC 130.5oC XXX -20.75oC

1 m sucrose

162oC 213oC 187.5oC XXX 36.25oC

3 m urea XXX XXX XXX -5.5oC 5.5oC

Figure 2.

GUIDE QUESTIONS: ( PART B)

1.) How does the nature of the solute affect the colligative properties, i.e, boiling point, freezing point, and

osmotic pressure of the solution?

ANSWER:

The nature of solute does not affect the colligative properties. Colligative properties are dependent on the amount of solute.

2.) What is the significance of the Van’t Hoff Factor? Account for the difference in the values of the

theoretical and the experimental Van’t Hoff Factor for NaCl.

ANSWER:

The Van’t Hoff factor accounts for the dissociation of the electrolyte solutes into ions increasing the solute particle concentration. The experimental Van’t Hoff factor is different from the theoretical value because the theoretical value assumes that the ions act independently in a solution, which is achieved only in extremely dilute solutions where the interaction between cations and anions is minimal. Cations and anions interact in more concentrated solutions resulting to an experimental Van’t Hoff factor with a value less than that of the theoretical.

3.) Why do green mangoes lose water and shrink when prickled in brine solution?

ANSWER:

Due to osmosis (the movement of water from a solution of lower solute concentration to one of higher solute concentration), water in green mangoes move to the brine solution which has a higher concentration. Thus, the green mangoes shrink and lose water.

4.) Calculate the freezing point of a 50% aqueous solution of ethylene glycol [ C2H4(OH)2 ] using the Kf of water which is

1.86oC/modal.

100g of solution(50%) = 50 gMW of C2H4(OH)2 = 60 g50 g (1 mol / 60 g) = 0.0806 mol 50 g = 0.05 kgM = mol of solute / kg of solventM = 0.0806 mol / 0.05 kgM = 16.12 molal

ΔTf = KfmΔTf = (1.86°C/m)(16.12m)ΔTf = 30°C Tf = 0°C – 30°CTf = -30°C

5.) The boiling point of pure acetone (Kb = 1.7oC/m) is 56.50oC. What is the boiling point of a 0.100 m solution of

a non-volatile non-electrolyte solute in acetone?

ANSWER:

ΔTb = KbmΔTb = (1.7°C)(0.100m)

ΔTb = 0.17°C

Tb = 56.50°C = 0.17°CTb = 56.17°C

Conclusions

•Polar liquids tend to dissolve readily in polar solvents. Nonpolar liquids tend to be insoluble in polar liquids.

•Solubility of most solid solutes in water increases as the temperature of the solution increases.

•The solubility of gases in water decreases with increasing temperature.

•The solubility of a gas increases in direct proportion to its partial pressure above the solution.

Conclusions

•In concentrated solutions, cations and anions interact more, resulting to an experimental Van’t Hoff factor different from that of the theoretical.

Solutions Ppt

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