BIOCHEMISTRY SBK3013

LAB PROJECT 1: APPLICATION: MAKING pH INDICATOR

MAUREEN SANTIH ANAK AMBANG	D20141067070
SHARIFAH AWANIS BINTI SYED MOHD ASWAD	D20141067053
HEIDI AMELDA ANAK LAGAT	D20141067086

DATE OF EXPERIMENT: 10 MARCH 2017

LECTURER:  DR ROSMILAH BINTI MISNAN

INSTRUCTOR: NUR ATIEKAH BINTI AZAHARI

LAB PROJECT 1: APPLICATION: MAKING PH INDICATOR

Introduction:

A pH indicator is a substance which has one colour when added to an acidic solution and a different colour when added to an alkaline solution. A pH indicator measures whether a substance is acidic or basic, and some indicators can also measure how acidic or basic it is. When the indicator comes in contact with a substance, the indicator's colour corresponds to that substance's approximate pH, which is a scale of zero to fourteen with zero being the most acidic, seven being neutral, and fourteen being the most basic that indicates the acidity or basicity of a substance. In this experiment we make an indicator from red cabbage. The experiment is in two parts. The first part involves some red cabbage. In the second part, we test our own indicator.

Materials:

      i.        0.1 M HCl solution (add 8.3 mL of concentrated HCl solution to enough deionized or distilled water to make 1.0 L of solution)*

     ii.        0.1 M NaOH solution (dissolve 4.0 g NaOH in enough deionized or distilled water to make 1.0 L of solution)*

      iii.        2-propanol (isopropyl alcohol) /acetone /deionized or distilled water

      iv.        Purple cabbage

     v.        Fruits/vegetables/flowers- EACH GROUP HAS TO BRING ANY ONE.

Extracting the indicator

   1. Plant parts that are most pigmented was selected.

For flowers, only a few petals are normally needed. For fruits and vegetables, finely chopped pieces should be used. Use only that portion of the fruit or vegetable that is most pigmented.

   2. 10 mL of solvent and macerate was added.

   3. The plant parts was crushed with mortar and pestle and left for 15 minutes to enhance the extraction.

Suggested solvents: water, 2-propanol, 50-50 water/2-propanol mixture, or acetone. One of these should easily extract the colour. If the extracts are very dilute, the colour can be concentrated by heating the opened bag in a warm water bath or by pouring the extract in a beaker and evaporating on a hot plate.

4. The filtrate from the macerated plant samples is filtered and collected.

Testing the pH range of the indicator

1. 13 test tubes was labelled from 1 to 13.

2. 9.0 mL of distilled or deionized water was placed in all test tubes except #1, #7 and #13.

3. The solutions in the acid range was prepared in the following manner (Refer Table 1)

4. 10.0 mL of 0.1 M HCl was placed in test tube #1. (pH = 1)

b)    1.0 mL of 0.1 M acid was transferred from test tube #1 to test tube #2 and mixed thoroughly. (pH = 2)

c)    1.0 mL of acid solution was transferred from test tube # 2 to test tube #3 and mixed thoroughly. (pH = 3)

d. The making the serial dilutions was continued by transferring 1.0 mL of the most recently diluted acid solution to the next test tube until six acid solutions of pH 1 to 6 have been prepared. Be sure to mix each thoroughly before the transfer.

5. 0.0 mL distilled or deionized water was added to test tube #7. (pH = 7)

6. Solutions of base was prepared in the following manner:

a.    10.0 mL of 0.1 M NaOH was placed in test tube #13. (pH = 13)

b.    1.0 mL of 0.1 M NaOH was transferred from test tube #13 to test tube #12 and mixed thoroughly. (pH = 12)

c.    The making serial dilutions of the base was continued from pH 12 down to pH 8 by transferring 1.0 mL of the most recently diluted basic solution to the next test tube and mixing thoroughly each time.

Test tube	Distilled water	Acid or Base	pH
1	-	10 ml of 0.1 M HCl	1
2	9 ml	1 ml acid from test tube 1	2
3	9 ml	1 ml acid from test tube 2	3
4	9 ml	1 ml acid from test tube 3	4
5	9 ml	1 ml acid from test tube 4	5
6	9 ml	1 ml acid from test tube 5	6
7	10 ml	-	7
8	9 ml	1 ml NaOH from test tube 9	8
9	9 ml	1 ml NaOH from test tube 10	9
10	9 ml	1 ml NaOH from test tube 11	10
11	9 ml	1 ml NaOH from test tube 12	11
12	9 ml	1 ml NaOH from test tube 13	12
13	-	10 ml of 0.1 M NaOH	13

6. The wells of a spot plate was labelled from 1 to 13. Transfer a few drops of each of the solutions prepared in steps 3, 4, and 5 to the corresponding well in the spot plate.

7. A drop or two of the flower/fruit/vegetable extract was added indicator to each well. The pH at which the indicator changes colour was observed and recorded.

Results:

Red gabbage

Red flower

Testing the pH of other liquids

Once the pH ranges of the indicators have been determined, they can be used in acid-base titrations or to test the pH of household chemicals (Each group has to bring several household chemicals to be tested).

Results:

Before

 After

Using red gabbage extract:

Substance	Colour change after 3 drops of extract	pH value
Detergent	Purple	8
Vinegar	Pink	2
Axion (dish wash)	Dark green	13
Hand wash gel	Dark green	13
Shower gel	Orange	14

Using flower extract:

Substance	Colour change after 3 drops of extract	pH value
Detergent	Brown	9
Vinegar	Orange	2
Axion (dish wash)	Dark green	13
Hand wash gel	Red	1
Shower gel	Blue	10

Discussion:

In this experiment, we have made the pH indicator by using the red cabbage given and our own red flower. We made the indicator to indicate the pH value and the colour of our household substances when we drop cabbage extract and flower extract that we have done before.

As a results, when we drop the cabbage extract into detergent, the colour of the detergent change into purple colour. We compare the colour of the detergent with the pH indicator that we have done. The pH indicator indicate that the detergent have the pH value of 8. For the axion, the colour changed into dark green so the pH value showed by the pH indicator is 13 which is basic. As for vinegar, the colour of vinegar changed into pink colour. So, the pH value of vinegar is 2 which means acidic. Hand wash gel gives colour changed into red colour so the pH value showed by the pH indicator is 13 which is it shows acidity. Lastly, shower gel changed into blue colour when we drop the cabbage extract. This show that the pH of shower gel is 14 which means basic substances.

For the second set, when we drop the flower extract into detergent, the colour of the detergent change into brown colour. We compare the colour of the detergent with the pH indicator that we have done. The pH indicator indicate that the detergent have the pH value of 9. For the axion, the colour changed into dark green so the pH value showed by the pH indicator is 13 which is basic. As for vinegar, the colour of vinegar changed into orange colour. So, the pH value of vinegar is 2 which means acidic. Hand wash gel gives colour changed into dark green so the pH value showed by the pH indicator is 1 which is it shows basicity. Lastly, shower gel changed into blue colour when we drop the cabbage extract. This shows that the pH of shower gel is 10 which means very basic.

Conclusion:

The purpose of this experiment is to determine the pH value of the different household substances by using the pH indicator that we done it by using red cabbage extract and flower extract.

Reflection:

Sharifah awanis: from this experiment, I manage to identify the pH value of the household substance that we bought from our house itself. It is an interesting experiment because we manage to identify our surrounding household and we do not use constant substances for each group. So, the result of each group will be different. Moreover, we also learned how to prepare our own pH indicator in this experiment. Although the procedure in making the indicator are quite complicated, but we manage to do it in a group because we cooperate to complete this experiment.

Heidi amelda: From this experiment, I have learnt to be more efficient in conducting the experiment in a group on next time. The instructor also has given a clear instructions for us. I have a great group mates because they gave a great teamwork during conducting the experiment. I am happy to work with them even though we have some problem during the experiment. Overall, everything is fine.

Maureen santih: I like the color changes that happen during testing the pH range of the indicator experiment. But I quite confused during preparation of the solutions because they required transferring of liquid into a lot of test tubes. Fortunately,the instructor guide my team patiently. Overall, I like the experiment.