Page 25 - Chemistry - XI

pH of Vegetable and Fruit Juices

S. pH paper Universal Indicator
No. Sample Colour produced pH Colour produced pH

1. Lemon juice

2. Tomato juice

3. Orange juice
4. Pineapple juice

Results

pH of lemon juice is ________ and is acidic/basic/neutral.
pH of tomato juice is ________ and is acidic/basic/neutral.

pH of orange juice is ________ and is acidic/basic/neutral.
pH of pineapple juice is ________ and is acidic/basic/neutral.
pH of solution in test tube 1 is _____ , 2 is _____ , 3 is _____ , 4 is _____ , 5 is _____ , and 6 is _____ .

Precautions
1. Equal number of drops of the universal indicator should be added in each test tube.
2. The colour of the solution should be matched very carefully with the pH chart.

VIVA VOCE

Q1. Defi ne pH.
Ans. pH is defi ned as negative logarithm of [H O ].
+
3
Q2. What is meant by pH paper?
Ans. pH paper is a strip of paper which is prepared by dipping the strip in the solutions of diff erent
indicators and then drying them.
Q3. What is pH of pure water at 298 K?
Ans. pH = 7

Q4. What is use of pH paper?
Ans. It is used to determine the approximate pH of solutions.

Q5. What is meant by universal indicator solution?
Ans. It is prepared by mixing a number of common indicators together so that the mixture obtained can
pass through a series of changes over a much wider pH range.
Q6. Out of lemon, apple, orange, pineapple which juice is the least acidic?
Ans. Orange juice with pH=3.9

Q7. If we dilute each juice, what will be the change in pH value?
Ans. pH value will increase.
23