Universal Indicator

Groupmates:

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

Introduction

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

Aims

  Explore  Extraction of natural indicators  Color change Determine  Which plant can be an indicator  Which can cover the pH range

Precautions

 Goggles 

Water bath

 Prevent direct heating

Apparatus and Chemicals used

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

Procedures

     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

Result

Hibiscus Methyl Orange & Phenolphthalein

Result

Discussion



1.

   Questions

Why hibiscus can as the indicator for different pH ?

Contains anthocyanine [1,2] Pigment  Pink, red, purple, violet and 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

Discussion

3.

Any differences between the efficiency of hibiscus and phenolphthalein ?

Hibiscus indicator Different pH values

of the testing solutions Different colors in these solutions Sharp color change  Easy to detect end-point

Phenolphthalein

Cannot shows the pH

values

Acidic  Colorless Alkaline  Pink Gradual color change  Uneasy to find the end-point

Discussion

 1.

2.

Error & Improvement Experiment was carried out once only  Carried again  Raise the accuracy Titration has not been carried out  Titration should be carried out   With methyl orange, phenolphthalein and hibiscus indicator respectively Color change can be observed

Discussion

3.

Only parts of flowers & fruits crushed to make indicators  Should be crushed more times  Should be used twice by one

titration

Discussion

4.

Conc. of flowers & fruits in indicators for color change not investigated  Different conc. of the flowers and  fruits in indicators Different effects on color change  Indicator of different conc. should be prepared in each titration

Discussion

5.

Solution extracted in foam state  Not pure enough  Affected color change

Discussion

 Limitation  Inaccurate equipment for extracting pure solution

Conclusion

 

Hibiscus

 Universal indicator Distinct color changes

Reflection

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

Universal Indicator

The End