Experimental Analysis of Simple and Fractional Distillation: Identifying Unknown Compounds and Assessing Distillation Efficiency

Categories: Chemistry

Analysis, Pages 3 (515 words)

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The aim is to conduct experiments on both simple distillation and fractional distillation using a known sample. Based on the gathered data, distillation curves will be plotted for both methods. Additionally, a fractional distillation will be performed on an unknown sample to isolate two compounds and determine their identities and percent concentrations.

Results and Discussion:

In the simple distillation experiment, a (1:1) mixture of toluene and cyclohexane was utilized. As a modification, 35 mL of each instead of 30 mL was used. Temperature readings were recorded after every mL of the sample was collected.

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The data collected from this experiment is summarized in the table below.

Volume (mL)	Temperature (⁰C)	Volume (mL)	Temperature (⁰C)	Volume (mL)	Temperature (⁰C)
1	69	21	51	41	65
2	71	22	51	42	65
3	75	23	51	43	66
4	76	24	53	44	66
5	78	25	54	45	66
6	79	26	55	46	66
7	75	27	56	47	66
8	71	28	58	48	67
9	68	29	60	49	67
10	65	30	61	50	68
11	62	31	61	51	68
12	59	32	61	52	68
13	54	33	62	53	69
14	50	34	63	54	67
15	49	35	62	55	66
16	48	36	64	56	66
17	48	37	64	57	66
18	49	38	65	58	67
19	50	39	65	59	68
20	50	40	65	60	66

The graph generated indicates a gradual temperature increase during distillation. However, upon comparison with literature, discrepancies were observed. Plateau regions were evident around 65 and 66°C, with a significant distillate collection between 65-68°C. These findings do not align with the expected solvent mixture, given that cyclohexane's boiling point is 80.

7°C, and toluene's is 110.6°C. The possibility arises that the actual mixture might be toluene and hexane or methanol and toluene, considering methanol boils at 64.7°C and hexane at 68.8°C. These values closely match the observed distillation temperatures.

Fractional Distillation:

In the fractional distillation of a (1:1) mixture of toluene and cyclohexane, 35 mL of each instead of 30 mL was used. Temperature readings were recorded after each mL of sample collection. The initial results were inconsistent, prompting two additional repetitions of the experiment. In the final run, the condenser was uncapped towards the end, leading to an extra 5 mL of distillate.

The data from the third experiment is tabulated below.

The temperature graph depicts a sharp temperature increase between 55 to 100 °C, with plateau regions at 55-56 °C and 100 °C. Analysis of the data suggests the presence of solvents with boiling points matching acetone (56.5 °C) and water (100 °C).

Post-lab insights:

The graph indicates the acquisition of a pure compound at temperatures ranging from 65 to 68 °C, but subsequent fractions beyond 68 °C show contamination with the second solvent.
Sodium chloride, a non-volatile substance, has a minimal impact on water's boiling point, especially in small quantities. Insoluble substances do not affect the boiling point, resulting in a vapor temperature of 100 °C.
Bonds in a substance do not break simultaneously; surface molecules, experiencing lower pressure, evaporate first.
The returning condensate contains a significant amount of high-boiling liquid, allowing lower-boiling substances to distill over.
Boiling causes liquid volume expansion, and in a sealed system, this can lead to increased pressure and potential explosion.
Faster distillation may overrun the first boiling point, introducing impurities into the second liquid.
Water droplets in the solvent mixture, observed due to their immiscibility with hydrocarbons, appear cloudy.
Water flow direction is typically aligned with vapor rising in the column, ensuring removal of warm water at the condenser top.

Conclusion: The unknown compounds match the boiling points of acetone and water. Although the obtained simple and fractional distillation curves deviate from literature standards, the overall trend is consistent. Fractional distillation demonstrates better separation due to an extended plateau, allowing thorough solvent distillation and reduced impurities.