Universal Indicator

Groupmates: Carmen Cheung (4) Chris Chow (7) Sandy Luk (21) Gary Ma (25) Hendrick Wong (28) Brian Wong (29)

Acid-base indicator color change with pH Detect acidity Detect acidity and alkalinity alkalinity Plant pigments colour dependent of pH

Introduction

Explore Extraction of natural indicators Color change Determine Which plant can be an indicator Which can covercover the pH rangepH range

Aims

Goggles Water bathWater bath Prevent direct heating

Precautions

Fruits - oranges, apples, grapes Vegetables - beetroot, spinach, cauliflower, ginger, chili Flowers – carnation, hibiscushibiscus

Mortar and pestle Test tube Test tube rack Beaker Dropper Ethanol Stirring rods

Deionized or distilled water 0.1M HCl (aq) (pH1) NaOH(s) 100cm3 and 10cm3 Measuring cylinder

Apparatus and Chemicals used

Preparing pH 1-14 solutions Extracting the indicator Testing the pH solutions with the

indicators prepared Testing the solutions with methyl

orange and phenolphthalein Comparing the color changes of the

indicators

Procedures

Result

 

Methyl Orange & Phenolphthalein

Hibiscus

Result

Discussion

Questions1. Why hibiscus can as the indicator

for different pH ? Contains anthocyanine [1,2]anthocyanine [1,2] Pigment

PinkPink, redred, purplepurple, violet violet and blue blue Dye extracted

Changes its colour Hydrogen ion conc. of the solution

Discussion

2. Why other substance used can only detect the pH of alkali ?

Equivalence point obtained Coincident the one by standard

indicator Flower extract Use of mixed indicator

Discussion3. Any differences between the efficiency

of hibiscus and phenolphthalein ?

Hibiscus indicatorHibiscus indicator PPhenolphthaleinhenolphthalein

Different pH valuesDifferent pH values of the testing solutions

Cannot showsCannot shows the pH pH valuesvalues

Different colorsDifferent colors in these solutions

Acidic ColorlessAlkaline Pink

SharpSharp color change Easy to detect end-point

GradualGradual color change Uneasy to find the end-point

Discussion Error & Improvement1. Experiment was carried out oncecarried out once only Carried againagain Raise the accuracy2.2. TitrationTitration has not been carried out TitrationTitration should be carried out With methyl orange, phenolphthalein and hibiscus indicator respectively Color change can be observed

Discussion

3. Only parts of flowers & fruitsparts of flowers & fruits crushed to make indicators

Should be crushed more timescrushed more times Should be used twiceused twice by one one

titration titration

Discussion

4.4. Conc. of flowers & fruitsConc. of flowers & fruits in indicators for color change not investigatednot investigated

Different conc. of the flowers and fruits in indicators Different effectsDifferent effects on color change Indicator of different conc. should be prepared in each titration

Discussion

5. Solution extracted in foam state foam state Not pureNot pure enough Affected color change

Discussion

Limitation Inaccurate equipmentInaccurate equipment for extracting

pure solution

HibiscusHibiscus Universal indicator Distinct color changes

Conclusion

Poor time management Poor preparation A gain of knowledge Deeper interest in Chemistry

Reflection

The End

Universal Indicator