Affecting the Boiling Point of Miscible Mixtures of Solvent – Lab Report Example

Design Lab: Investigate On Chemistry Related Factor Affecting the Boiling Point of Miscible Mixtures of Solvent Introduction A simple definition of boiling point is the temperature at which a substance or an element changes from its liquid state to a gaseous state. There are factors that affect the boiling point of substances but in this case, miscible mixtures of solvents will gain more attention. The experiment will focus on the effect of chemistry related factor on the boiling point of miscible mixtures of solvent.
Aim
The aim of the experiment is to determine what chemistry related factor affects the boiling point of miscible mixtures of solvents.
Design
Research Question
The experiment will mainly focus on the chemistry related factor that affects the boiling point of miscible mixtures of solvents; this is the research question that the experiment will attempt to answer. The most important variable in this experiment is the change in the concentration of the miscible mixture of solvents.
Hypothesis
Change in the concentration of the miscible mixture of solvents changes its boiling point.
Variables and its Control
There is only one variable in this experiment and it is the change in concentration of the miscible mixture of solvents. The change in boiling point will be determined using the van’t Hoff factor which determines temperature elevation when a solute is added to a solvent. The variable will be controlled using a known concentration of a mixture of miscible solvents. The controlled variable will assist in identifying any slight variations in the experiment that may affect the credibility of the outcome.
Apparatus
Thermometer
Heat source
Boiling flask
A stirring rod
A weighing balance
Measuring cylinder
Spatula
Labels
Chemicals
Sodium chloride (NaCl)
Water
Method
1) Weigh 20 grams of NaCl and add it to 100ml of water. Label it as the first mixture.
2) Stir until all NaCl dissolves in the water.
3) Boil the mixture.
4) Calculate its molality.
5) Record its temperature.
6) Weigh 40 grams of NaCl and add it to 100ml of water. Label it as the second mixture.
7) Stir until NaCl dissolves completely.
8) Calculate its molality.
9) Boil the mixture and record its temperature.
10) The temperature results from the two experiments will be compared and evaluated to see whether an increase in concentration affects the boiling point of the mixture of miscible solvents.
Data Collection and Processing
The molality (m) of NaCl is calculated using the formula
Moles of NaCl = 20g × 1 mol/ ([Atomic mass of Na = 23] + [Atomic mass of Cl = 35.5])
Moles of NaCl = 20g × 1 mol/58.5g
Moles of NaCl = 0.34 mol
Kg water = Density × Volume
Kg water = 0.994 g/ml × 100ml × 1kg/1000g
Kg water = 0.099 kg
Therefore,
The molality of the first mixture is 3.434 mol/kg
The molality for the second mixture is as follows:
Moles of NaCl = 40g × 1 mol/ ([Atomic mass of Na = 23] + [Atomic mass of Cl = 35.5])
Moles of NaCl = 40g × 1 mol/58.5g
Moles of NaCl = 0.68 mol
Kg water = Density × Volume
Kg water = 0.994 g/ml × 100ml × 1kg/1000g
Kg water = 0.099 kg
Therefore,
Calculating the van’t Hoff factor for the first mixture:
∆T = iKbm
∆T = 2 (NaCl dissociates into two ions, Na+ and Cl-) × 0.51 °C kg/mol (this is the Kb for water) × 3.434 mol/kg
∆T = 3.5 °C
Calculating the van’t Hoff factor for the second mixture:
∆T = iKbm
∆T = 2 (NaCl dissociates into two ions, Na+ and Cl-) × 0.51 °C kg/mol (this is the Kb for water) × 6.869 mol/kg
∆T = 7.0 °C
Conclusion and Evaluation
From the results, it is evident that an increase in molality (the concentration of the mixture) leads to an increase in the boiling point. In other words, an increase in concentration increases the boiling point of the mixture. Thus, for the purposes of this experiment, change in the concentration of the miscible mixture of solvents changes its boiling point. The greater the concentration, the greater the elevation of the boiling point.
It is imperative to note that there could be errors resulting from wrong measurement of the chemicals; this can happen especially when the weighing balance is poorly calibrated. If the thermometer is poorly held, false temperature readings can be recorded. One must ensure that the weighing balance is properly calibrated and the thermometer should be held in the right way.