Question

When drops of lemon juice are put on
blue litmus it turns red what will happen
if you put some drops of soap solution
on the same position on litmus paper?

SCERT Class 7 Telangana, Physical Science Chapter 2 Acids And Bases

Answer 1

in first solution it turns red because lemon juice is citric acid and in second I think that the soap is acidic. l know that the soap is basic but sometimes it will be acidic or neutral

Answer 2

Answer:

This test with litmus paper is a test for acids and bases.

Litmus being a natural dye and indicator turns the color to red/ blue. When drops of lemon juice are put on blue litmus it turns red because of presence of acids.

Now, when we will put some drops of soap solution on the same position i.e. on red litmus paper then the color of the litmus will change to blue. The reason being, that bases turn red litmus blue and soap solution is a base.

If soap solution is put on a blue litmus paper, its color will not change because bases do not change the color of blue litmus and soap solution is a base.