Question

You are provided with three test tubes A, B and C as shown in Figure with different liquids. What will you observe when you put (a) a piece of blue litmus paper in each test tube. (b) a piece of red litmus paper in each test tube. (c) a few drops of phenolphthalein solution to each test tube.

Solution of Soap solution Pure water

Answer 1

Acid-base Indicators

• Litmus paper is a type of paper that changes color when dipped in acidic solutions and can therefore be used to measure acidity.
• Under acidic conditions, blue litmus paper turns red, whereas red litmus paper turns blue under basic or alkaline conditions.
• Phenolphthalein is colorless by nature but becomes pink in alkaline solutions.
• Phenolphthalein is an acid-base indicator used to determine a solution's pH.

Observations

• The solution of tartaric acid is acidic and is kept in test tube A.
• The soap solution is basic and is kept in test tube B.
• Pure water is neutral and is kept in test tube C.
• The given figure is as follows:

Indicators	Test tube A	Test tube B	Test tube C
Piece of blue litmus paper dipped in the solution	Turns red	Remains Blue	Remains blue
Piece of red litmus paper dipped in the solution	Remains red	Turns blue	Remains red
Few drops of phenolphthalein added to the solution	Colorless	Pink color	Colorless