Universiti Tunku Abdul Rahman (Kampar Campus)

Faculty of Science, Engineering, and Technology

Bachelor of Science (Hons) Biotechnology

Year 1 Semester 2

Laboratory 1B (UESB 1212)

(II) The Properties of Matter

Lecturer: Ms. Chew Yin Hoon

Student’s Name: Cheah Hong Leong

Student’s ID: 08AIB03788

Partner’s Name: Chong Shi Fern

Partner’s ID: 08AIB02580

Experiment No. 6

Title: Extraction: Extraction with Acid and Alkali

Date: 13 March 2009

Title: Extraction: Extraction with Acid and Alkali

Objective:

- To determine the percentage of recovery of the benzoic acid and dichlorobenzene

extracted from the ether solvent and aqueous solvent.

- Determine the melting point of the extracted dichlorobenzene.

Results:

Weight of starting dichlorobenzene = 1.0178g

Weight of starting benzoic acid = 1.0016g

Volume of ether = 40 ml

Volume of NaOH added before first separation = 20 ml

Volume of NaOH added before second separation = 10 ml

In aqueous solution,

Weight of filter paper = 0.9817g

Weight of filter paper and recovered benzoic acid solid = 2.4670g

Weight of recovered benzoic acid solid = 1.4799g

In organic solution,

Weight of watch glass = 28.8334g

Weight of watch glass and recovered dichlorobenzene = 28.9601g

Weight of recovered dichlorobenzene = 0.1267g

Melting point of dichlorobenzene = 53 oC

Analysis and Calculation:

Percentage of recovery=Weight of recovered solidWeight of starting solid

x 100 %

Percentage of recovery of benzoic acid = (1.4799g/1.0016g) x 100%

= 147.75%

Percentage of recovery of dichlorobenzene = (0.1267g/1.0178g) x 100%

= 12.45%

Discussion:

Percentage of recovery of benzoic acid was more than 100% which is impossible. The

most possible reason causing this was the incomplete hydration of benzoic acid. The

weight of the benzoic acid solid obtained was not the actual weight of the recovered

benzoic acid. Most of the weight obtained was contributed by unhydrated water that still

remained in the solid.

In contrast to the percentage of recovery of benzoic acid, percentage of recovery of

dichlorobenzene was too low, only 12.45%. Most of the starting dichlorobenzene was not

recovered from the solution. Another possible reason that leads to this percentage was the

drying of the solid in fame hood. During the drying of this solid in fame hood, some of

the solid in watch glass was moved out of the watch glass by the air flow in fame hood.

Conclusion:

The percentage of recovery of benzoic acid was unknown.

The percentage of recovery of dichlorobenzene was 12.45%

The melting point of dichlorobenzene was 53 oC.