English Resume: The Results of a Report from a Simple Chemical Experiment

pH Scale and Usage Indicator

Theoretical basis

The concept of acids and bases is based on several properties which are represented by a group of their aqueous compounds. Based on the properties shown, the acid is a compound that has a sour taste, and redacts the blue lacmus. Bases are compounds that have a bitter taste, and can brighten the red litmus. In aqueous solution, the acid produces H⁺ and alkaline ions to produce OHˉ ions (Basic Chemical Practicum Guide, 2012: 56).

The ion concentration [H⁺] and the concentration of [OHˉ] in water, acid or base solution are very small numbers. Therefore, a chemist named Sorensen proposes a concept called PH (P means Potential and H is a symbol of the Hydrogen element) PH is defined mathematically as follows: PH = - Log [H⁺]

For PH in the environment:

Ø  Acid: PH <7

Ø  Bases: PH> 7Neutral: PH = 7

(Tony Bird, 1987: 71)

Acids and bases are chemicals that are present in everyday life. Citrus juice and vitamin c are none other than ascorbic acid. In our stomach there is a sap for digestion containing hydrochloric acid (HCl). Acetic acid, a vinegar acid widely used in cooking kitchens, carbonic acid is present in soft drinks and to provide fresh flavor and sulfuric acid widely used in the battery. They are examples of acid around us. The base around us is the ammonia used as a solvent that has a strong odor. To be able to know the acidic or alkaline solution, usually using the PH indicator, generally most of the frequently used Lakmus (Benny karyadi 1997: 67-66).

Acids and bases according to arrhenius. Acid is a compound dissolved in water increasing the concentration [H⁺] and the base is a compound that increases the concentration of [[OHˉ] (David.W Oxtoby, 1998: 29).

The occurrence of acid: some non-metallic element oxides can react with water and produce acids called acid oxides.

Reaction Example: SO₂ + H₂O ₂ H₂SO₃ = Sulfite Acid

SO₃ + H₂O ₂ H₂SO₄ = Sulfuric acid

(Soehito, 1997: 78 - 79)

The strength of the acid can be measured and compared through the value of its protolisis equilibrium constant. For protolisis of acetic acid the equilibrium constants can be expressed as follows:

Ka = [H⁺O⁺] [CH₃COOˉ] / [CH₃COOH]

This formula is identical to the ionization constants defined and described. The acid protolisis in water can be described by a general equation:

Acid + H₂O ₃ H⁺O⁺ + Bases

Thus, Ka = [H⁺O⁺] [Base] / [Acid]

The bigger the ionisai constant, the stronger the acid, and consequently the weaker the bases. Thus, Ka's value is the same as a measure of base strength (G.Svahite .1990: 98-199).

Tools and Materials

Ø  Test tube

Ø  Drop pipette

Ø  Tube shelf reaction

Ø  Indicator

Ø  PH meter

Ø  Electrode

Ø  SpatulaHCl 0.01 M

Ø  Distilled water

Ø  NaOH 0.01 M

Ø  Indicators (methyl orange, phenolphthalein, blue bromtimole, yellow alizarin, methyl red)

Ø  PH of various substances (Vinegar solution (dilute 10X), Grape / citrus, carbonated beverage (dilute 50%), Shampoo, Liquid detergent (5% solution), Ammonia for Household, Soda kue (10% solution), Aspirin Tablet (salicylic acid dissolved in 20ml water)}

Work Procedures

A.    Acid region pH 2 to 6

Standard HCl solution 0.01 M (pH = 2)

·         Put in a test tube

·         Taken 1 M

·         Diluted with 9 mL of distilled water

·         Stirred slowly

HCl solution pH = 3

·         Taken 1 mL

·         Put in 2nd test tube

·         Diluted with 9 mL of distilled water

·         Stirred slowly

The HCl solution pH = 4

·         In the same way pH solutions 5 and 6 are prepared

Results

B.     Neutral region pH 7

Water that has been boiled

·         Put in a test tube

Results

C.     Base region pH 8-12

NaOH 0.01 M (pH = 12)

·         Put in a test tube

·         Diluted 1mL with 9 mL of boiled water

·         Stirred

·         NaOH solution pH = 11

In the same way made pH 10, 9, and 8

·         1 mL of each solution is made of parts A, B, and C

·         Labeled every solution according to pH

·         Dripped 1 drop of indicator on each test tube up change color

·         Observed and recorded color change indicator at each pH

·         The indicator used successively is methyl orange, Phenolphthalein, blue brontimol, yellow alizarin, and methyl red

Results

D.    The pH indicator of various substances

a.     Vinegar solution (diluted 10')

b.     Grape / orange juiceBicarbonate Drink (diluted 50%)

c.     Shampoo

d.     Liquid detergent (5% solution)

e.     Ammonia for household purposes

f.     Baking soda (10% solution)

g.     Tablet Aspirin (salicylic acid dissolved in 200 mL water)

2 mL each solution is inserted into each test tube

·         Dropped 2 drops of indicators that have been provided into the Each test tube

·         Compared color with standard solution

·         Specified pH according to color

Results

E.     Determination of pH by using pH meter

·         PH meter

·         Calibrated

·         Electrode is dipped into standard solution

·         Recorded pH meter reading

·         Results

Research Data

No	Sample	Indicator Type
		MO	MR	YA	PP	BB	PH	Information
1	Vinegar Solution	O	Pi	Y	NC	Y	< 3,1
2	Grape and Orange Juice	O	R	Y	Y	R	3,1- 4,4
3	Sprite	O	Y	NC	NC	R	3,1 - 4,4
4	Shampoo	Y	R	G	G	Y	10 – 12
5	Liquid Detergen	G	Y	B	Pi	G	6,2 - 7,6
6	Amonia RT	Y	Y	NC	NC	Y	4.6 - 6,0/6,7 - 8,3
7	Cake Soda	O	Y	Pu	Pu	B	3,1 - 4,4 / 6,7 - 8,3
8	Aspirin	R	R	Y	NC	Y	< 3,1

Information:

Ø  MO       : Methyl Orange

Ø  MR       : Methyl Red

Ø  YA        : Yellow Alizarin

Ø  PP         : Fenolftalein

Ø  BB        : Bromtimol Blue

Ø  O          : Orange

Ø  R          : Red

Ø  G          : Green

Ø  Y          : Yellow

Ø  Pi         : Pink

Ø  Pu         : Purple

Ø  NC        : No Color

Conclusions

Based on the Practicum that has been implemented, as for the conclusions obtained are:

Ø  Acid and basic standard solutions can be obtained by various concentrations when the concentrations are known to be initial concentration and initial PH. This solution can be formed by dilution in the starting solution

Ø  The PH measurement of the solution can use various indicators by observing the color change in the solution and comparing the color we can determine its PH.

Ø  PH measurements can also be performed using a device PH meter which, when dipped, will show the PH by the number / value that exits on the device.

Ø  In the indicator it will show its PH based on the changing color of the acid or base solution. And if the solution is acidic it will give a different color to the base.

Ø  In this lab we can know that:

·         PH acid      → PH < 7

·         PH neutral → PH = 7

·         Basic PH     → PH > 7

References

Bird, Tony. 1987. Kimia Fisik. Jakarta; Erlangga.

Epinur dan M. Dwi Wiwi.E. 2012. Penuntun Praktikum Kimia Dasar. Jambi; Jambi University

Karyadi, Benny. 1997. Kimia Untuk Universitas. Bandung; Cipta Aditya Bakti.

Oxtoby, W. David.1998. Kimia Modern. Bandung; Bumi Aksara.

Soehito. 1975. Penuntun Praktikum Kimia. Bandung; Yudhistira.

Stevia, G. 1990. Analisis Anorganik Kualitatif. Jakarta; Vagel.