Beetroot as an indicator

1. BEETROOT AS AN INDICATOR Group Members : Asela Chamali Dhammika Dunhinda Nuwan Oshadi Pulasthi Saminda Sudeera R 13

2. CONTENT What is a pH indicator and its PH range…. Preparation of the Beetroot indicator and identification of its pH range. Applications of acid-base titrations. Discussion. Conclusion. References.

3. What is a pH indicator? Its pH range A pH indicator (An acid-base indicator ) is either a weak acid or weak base that exhibits a color change as the concentration of hydrogen (H + ) or hydroxide (OH - ) ions changes in an aqueous solution. Examples: Thymol Blue, Phenolphthalein, Methyl Orange, Bromocresol Green, B romophenol Blue and etc;  An Indicator’s colour change occurs over a range of hydrogen ion concentrations. This range is termed the   colour change interval . It is expressed as the Indicator’s pH range . Reference: Anne Marie Helmenstine , Ph.D., (2011).  Acid-Base Indicators. Available: http://chemistry.about.com .

4. Ability of using Beetroot as an indicator Beetroot Red , is a red glycosidic food dye obtained from its aglycone , obtained by hydrolyzing the glucose molecule, Betanin . The colour of B etanin depends on pH . It is bright bluish-red , becoming blue-violet as the pH increases. Once the pH reaches alkaline levels Betanin degrades by hydrolysis, resulting in a yellow-brown colour . Moira Sheehan, Carol Chapman. (2003).  Make your own indicator. Available: http://www.pearsonschoolsandfecolleges.co.uk .

5. Procedure Preparation of the Indicator: 1. 300.0 g of chopped Beetroot was added to 50.00 cm 3  of boiling water in a beaker and was boiled continuously for 45 minutes. 2. After allowing the beaker to cool for 15 minutes, boiled B eetroot were squashed and the liquid was filtered. 3 . The residues were squeezed once again and the liquid was evaporated to get a highly concentrated portion of the indicator.

6. Detection of the pH range : A series of solutions in the range pH 1.0 -13.0 was prepared by using 1.0 M NaOH and 1.0 M HCl acid. When the indicator was added the to the prepared series of solutions the colour was changed from red to yellow in between pH 10.0 -12.0. In order to get the exact pH range , another series of solutions was prepared by diluting the pH 10-12 solution range into 10.10, 10.20,……..,12.00 and 0.05 ml of the indicator was added to each solution. A colour change was observed in the pH range 10.80-11.20 , which is the working pH range of Beetroot .

7. Applications of titrations ii) Strong Acid – Weak Base Titration Colour Change: Red Yellow A colour change was not observed. i ) Strong Acid – Strong Base Titration

8. iii) Weak acid – Strong Base Titrations With 0.1M NaOH With 0.001M NaOH . A colour change was not observed . Colour Change: Red Yellow

9. Discussion A colour change was observed only in strong acid – strong base titration and weak acid-strong base titration (with 0.10 M NaOH), as the working pH range of the indicator falls to the vertical portion of those reactions. But when the base is diluted, a colour change was not observed, as the pH range of the Beetroot indicator doesn’t fall within the rapid pH change of the reaction. Although a colour change was observed in above two titrations, the most applicable titration is weak acid-strong base titration , because the vertical portion of the reaction shifts upwards.

10. Conclusion Working pH range of BEETROOT is pH  10.80 - 11.20 (Above result was obtained on 28 th of March 2012 at 11.50 a.m. at B2 102 laboratory under the room temperature 27 C. ) BEETROOT is a good indicator. But it is not a very suitable indicator for laboratory experiments as it should be prepared at the time the experiment is done. The prepared indicator also cannot be kept for a long time as it is a biological sample . Acidic Basic RED YELLOW

11. REFERENCES Anne Marie Helmenstine , Ph.D., (2011).  Acid-Base Indicators. Available: http://chemistry.about.com . Last accessed 5th April 2012. Australian Broadcasting Corporation(ABC). (2007).  Teaching Science - Cool Chemistry(PH Indicator).  Available: http://www.abc.net.au . Last accessed 4th April 2012. Lange's Handbook of Chemistry , 8th Edition, Handbook Publishers Inc; 1952. Moira Sheehan, Carol Chapman. (2003).  Make your own indicator. Available: http://www.pearsonschoolsandfecolleges.co.uk . Last accessed 2nd April 2012. Volumetric Analysis , Kolthoff & Stenge , Interscience Publishers, Inc; New York, 1942 and 1947.

12. Thank You