The Effect of Dissolving Solids on Boiling Point – Sodium Chloride (NaCl)
Aim / Objective:
To investigate the effect of dissolved solids on boiling point
Dissolution is the process by which a solute forms a solution in a solvent. The solute, in case of solids, usually has a crystalline structure that breaks into separate atoms, ions, and molecules.
For liquids and gases, the molecules must be able to form a solution from the solvent. The outcome of this process is dependent on the thermodynamic energies involved such as heat of solution.
For ionic compounds, dissolution takes place when the ionic lattice breaks up and the separate ions are then solvated. This commonly takes place in polar solvents such as ammonia or water.
The solubility of ionic salts in water is determined by their degree of solvation of the ions by water with the solvent. As well as this breakdown of their lattice structure is due to their polarity or non-polarity mix with the solvent.
3 containers of 5g Sodium Chloride (NaCl), measuring cylinder, unknown solution, thermometer, Bunsen burner, spatula, tripod stand, wire gauze, conical flask.
Method / Procedure:
1. Fill the conical flask with 100cm3 of the unknown solution
2. Record the temperature of the unknown using the thermometer.
3. Set up water bath to boil and place the flask with the unknown into the water bath.
4. Record the temperature of the boiling unknown.
5. Remove the flame
6. Add 5g of NaCl to the flask replace the flame and heat to a boil
7. Record the temperature of the mixture
8. Repeat steps 5 to 7 until a total of 15g NaCl has been added.
9. Tabulate results and plot a graph of mass of salt vs temperature.
1. Define boiling point
>>>Boiling point is the temperature at which a liquid boils to form a gas or condenses to form a liquid.
2. Describe the effect the addition of salts had on the boiling point
>>> The boiling point increased as the grams of NaCl increased.
3. Describe the effects of pure and impure substances on boiling point
>>> Pure substances have fixed boiling and melting points while impure substances tend to lower the melting point and raise the boiling point.
4. Describe how NaCl affects the boiling point.
>>> The NaCl acts as an impurity thus raising the boiling point.
Sources of Error/ Limitations/ Assumptions:
1. Parallax Errors due to incorrect measurements and recording of temperatures.
2. Unclean apparatus leading to impurities in the unknown