THEORY:
A universal indicator or a ph paper contains a mixture of several acid base indicators and hence can show several colour changes over a Broad range of pH values. Hence, a universal indicator solution or a pH paper can be conveniently used to determine the approximate pH of any aqueous solution.
APPARATUS:
1) Test tubes
2) Measuring cylinder
3) Test tube stand
4) Glass rod
5) Droppers
6) pH papers
CHEMICALS:
1) Universal indicator
2) Fruit juices, natural water samples etc.
PROCEDURE I: (Using universal indicator)
i) Put 10ml of different juices or samples in different test tubes with the help of a measuring cylinder, and label them.
ii) Arrange the test tubes in a test tube stand and add 3 drops of universal indicator into each of them.
iii) Note the colour of each sample and compare with the colour chart given on the indicator bottle.
iv) Note down the approximate pH of each sample.
PROCEDURE II: (Using pH paper)
i) Put some amount of the different juices or samples in different test tubes and label them.
ii) Arrange the test tubes in a test tube stand and put 1 – 3 drops of each
sample on a piece of pH paper by means of a dropper or glass rod.
iii) Observe the colour developed on the paper and compare with the colour chart given on the paper box.
iv) Note down the approximate pH of each sample.
RESULTS:
| sample | Using universal indicator color produced in the solution | Using universal indicator Approx pH | Using pHpaper color developed in pH paper | Using pHpaper Approx pH |
| 1.Lemon juice | ||||
| 2. Tomato juice | ||||
| 3.Orange juice | ||||
| 4. Apple juice | ||||
| 5.Amla juice | ||||
| 6. Natural tap water | ||||
| 7.Soil water |