This report deals with a series of experiments that are investigating solubility and concentrations. The experiments are three and are outlined below.
1. This task involves designing an experiment whereby an unsaturated, saturated and super saturated are created. The task also determines the relationship between intermolecular forces, solubility, interactions between solute and solvent and polarity.
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Materials used:
50g Sugar,
Distilled Water.
Pan
Heat source
Stirring rod
Beaker
Teaspoon
Procedure
Put 500 ml of distilled water into a beaker; add a tea spoon of sugar (5.69g) to the distilled water, stir the water till all the sugar dissolves. Add another tea spoon of sugar into the distilled water and stir until all the sugar dissolves. Repeat this process until you notice some crystals settling at the bottom of the beaker. Once you notice crystals have begun to settle at the bottom of the beaker continue adding sugar until you notice that the sugar being added is not dissolving anymore. After this observation, take the beaker and heat it gently while adding the rest of the 50 g of sugar continue heating until all the 50g of sugar is dissolved. Do not let the solution boil as this will remove some of the water in the solution. After heating pick the beaker and place in a pan filled with cold water and let it cool for not more than two minutes. The beaker is expected to be clear before you remove it from the cold water.
|
Steps |
observations |
|
Add one tea spoon of sugar into the 500 ml beaker with water |
All the sugar dissolves in the water |
|
Add several tea spoons of sugar into the 500 ml beaker with water |
Some sugar dissolves but some of the sugar settles at the bottom of the beaker |
|
Add more teaspoons of sugar into the 500 ml beaker with water |
None of the sugar that is added into the water is dissolved instead the added sugar settles at the bottom of the beaker |
|
Heat the beaker gently while adding the remaining of the 50g of sugar, after which the solution is cooled |
The sugar dissolves into the water completely |
An unsaturated solution was formed when sugar was added into the beaker with 500ml of distilled water and completely dissolved after being stirred. A saturated solution was formed when sugar was being added into the beaker with 500ml of water and the some of the sugar dissolved while others settled at the base of the beaker. A supersaturated solution was created when sugar that was added did not dissolve at all instead it all settled at the bottom of the beaker. After heating the super saturated solution the sugar at the bottom began to dissolve, this is because the intermolecular forces of water became weaker and hence producing space between the intermolecular forces holding the water molecules together. This new spaces are able to accommodate the excess sugar which were not able to dissolve. The solubility of sugar also increases with increase in temperature. The solute is soluble in the solvent which is water.
2. This task entails designing an experiment to recrystallize sugar out of a solution.
Materials used:
1-2 grams of sugar
Graduated cylinder
Watch glass
Beaker
Flask
Rubber tong
Heating plate
Electronic balance
25ml of water
Procedure
The beaker’s weight is measured before starting, the beaker was 101.84g. After measuring the beaker some sugar is placed in the beaker and the weight is then measured. The 25 ml water is then poured into the beaker and mixed with the sugar. The beaker is then placed on the heating plate and heated to boil. The water will begin to evaporate and some crystals will be seen at the bottom of the beaker. After which, the beaker is set to cool for a short duration, after the cooling period the beaker is measured. This enables one to know the sugar that has been formed.
| Mass of sugar used. Must be between 1&2 grams | 1.07 grams |
| Mass of empty beaker before you start | 101.84 grams |
| Mass of beaker with recrystallized sugar | 102.91 grams |
| Mass of recrystallized sugar | 1.03 grams |
| Volume of water added to dissolve | 25mL |
The sugar once added into the water dissolves because sugar which is the solute is soluble in water which is the solvent. Once the solution is heated the intermolecular forces begin to weaken as a result of the increased kinetic energy of the molecules, the molecules begin to move at an increased speed this causes the liquid to form into a gas which is water vapour (Hirschfelder, 2009) . During the cooling of the heated beaker the particles found at the bottom at the beaker are sugar crystals.
3. This task entails creating a 0.25M solution of sugar water
Materials used:
Sugar 90 grams
Water 2 litres
Procedure
The sugar 90grams is mixed with 2 litres of water.
Sugar’s chemical formula is C 6 H 12 O 6
The meaning of Molarity refers to the moles of solute per litres of the solution. In this scenario we have to find the number of moles of solute present
The moles of solute = 90.0 grams /180 grams per mole of C 6 H 12 O 6
The moles of solute = 0.50 moles of sugar
Molarity = Moles/Litres
Molarity = 0.50 Moles/ 2.0 litres
Molarity = 0.25M
The Moles fraction = moles of solute / total moles in the solution
Moles Fraction= 0.5 moles/ 1.0
Moles Fraction= 5/10
Moles percent= 5/10 * 100
Moles percent = 50%
Parts per Million by mass = 1 ppm
Parts per Billion by mass = 0.001 ppb
References
Hirschfelder, J. O. (2009). Advances in Chemical Physics, Volume 12: Intermolecular Forces. Advances in Chemical Physics, Volume 12: Intermolecular Forces.
