Teoh Jia Jun
Name Student ID
1607253
No of Experiment
SOLUTI SOLUTION ON ─ CONSTR CONSTRUCT UCTIO ION N OF SOLUBI SOLUBILIT LITY Y CURVE FOR POTASSIUM CHLORATE 10
Date of Experiment
27 February 2017
Date of Submission
13 March 2017
Name of Lecturer
Ms Chang Chew Cheen
Practical Group
P3
Practical Sub-group
G4
Title of Experiment
Student ID
Group member name’s
1)
1606889
Kelly Teh Ka Ling
2)
1606599
Emmanuel John a/l Baptist
Title: Solution- Construction of solubility curve for potassium chlorate. Objective:
1. To calculate the solubility of a substance under variety of temperature. 2. To construct the solubility curve for potassium chlorate. Introduction: Solubility is a chemical property referring to the ability for a given substance, the solute, to
dissolve in a solvent. It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution. A solution is homogeneous mixture of two or more substances where the proportions of which may vary between certain limits.The following types of mixtures may form: 1. Gas in gas, 2. Gas in liquid, 3. Liquid in liquid, and 4. Solid in liquid. This experiment is performed to obtain a solubility curve for solid potassium chlorate in water at different temperature. A solubility curve relates the concentration of a saturated solution to temperature. Generally, we measure the solubility of a solute in an aqueous solution in grams of solute per 100 grams of water. Solutions are also a mixture of solvents and solutes. For example, a coffee is a solution, which the solute is the coffee powder and is dissolved in the solvent which is water. The solute and solvent can be either a solid, liquid or a gas. A solution forms when the attractive forces between the solute and the solvent are similar. For example, sodium chloride, NaCl, dissolves in water, and forms a polar solvent. When the water molecules collide with the ionic compound which is NaCl, the charged of the water molecule become attracted to the positive Na+ ions and Cl- ions. The water molecules surround the ions and the ions move into solution. The attraction between the water molecules and the ionic compound, NaCl, is called solvation. It will occur until all the crystal has dissolved and all the ions are distributed throughout the solvent.
Apparatus and Materials:
Solid potassium chlorate, Distilled water, Thermometer (100°C), Burette, Boiling tube, Hot plate, Beaker, Ice (if necessary), Experimental Procedures:
3.00 g of potassium chlorate was weighed accurately and placed into a boiling tube. 10.0 cm³ of water was added from a burette and a thermometer was placed into the boiling tube. Boiling tube was placed into a beaker of water. The water was heated and the content was stirred in the boiling tube gently with a glass rod until the solid has just dissolved completely. The boiling tube was removed from the hot water, and was allowed to cool in air with constant stirring. The temperature at which crystals start to form was noted in the boiling tube. The experiment was repeated, and the temperature was determined again. The average temperature was taken as the temperature at which the solution is just saturated. 5.0 cm³ more of water was added from the burette, and the temperature was determine as described above. The procedure was repeated until about 40.0 cm³ of water has been added. Result:
Volume of water/ ml
Temperature/ ℃
Mass of KClO3 per 100g H2O/ g
10
63
30.018
15
57
20.012
20
42
15.009
25
34
12.007
30
28
10.006
35
25
8.5766
40
20
7.5045
Discussion:
When determining the solution of a substance, we must know the heat of solution(ΔHsol), lattice energy and the heat of hydration(ΔHhydr ). Heat of solution is the total enthalpy change that occurs when a solution is formed from solute and solvent. Negative value of heat of solution indicates that the process is exothermic(releases heat) while positive value of heat of solution indicates that the process of dissolving of a substance is endothermic (absorbs heat). Heat of solution is one of the two factors that determine the solubility of a solute. Heat of hydration is the enthalpy change for the hydration of one mole of separated(gaseous) ions while lattice energy is the enthalpy change that occurs when one mole of ionic solid separates into gaseous ions which indicates the strength of ionic interaction in the solid. Most ionic solids have positive heat of solution because their lattice energy is greater than the heats of hydration. Thus, heat is absorbed to form a solution. This indicates that solids are more soluble at higher temperature. Rise in temperature causes the increase of solubility. In this experiment, the graph of the relation between solubility and temperature of KClO3 shows solubility increases when temperature rises. Our prediction is that the solubility will continue to increase if the temperature continues to rise. An important precaution must be taken in this experiment, which is the reading of temperature must be taken as soon as the salt crystals start to form. The crystallization of salt must be observed carefully.
Conclusion:
For many solids dissolved in liquid water, the solubility increases with temperature. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions. Reference:
1. Peter Hong Leong Cheah, (2009). Experiment 9 Short. Retrieved 11 March, 2017, from https://www.scribd.com/doc/18026424/Experiment-9-Short 2. University Of Tunku Abdul Rahman.2016. Solution-Construction of Solubility Curve for Potassium Chlorate. In. Lab Manual UDEC1134 Chemistry Laboratory I, Bachelor of Science (Hons) Chemistry, 2017, page 19-20.
