question_answer

You are provided with three test tubes A, B and C which contain distilled water, acidic solution and basic solution respectively. If you are given blue litmus paper only, how will you identify the contents of each test tube?

Answer:

(i) First take three strips of blue litmus paper and dip one in each test tube.

(ii) The liquid in test tube A turns blue litmus to red. It means test tube A contains acid because (acid turns blue litmus to red).

(iii) If other two test tubes do not change the colour of blue litmus paper, it shows that one of them contains a base and the other contains distilled water.

(iv) Now put the blue litmus paper which is turned red by the acid of test tube A in the remaining two test tubes.

(v) If the liquid of test tube B turns that red litmus paper to blue again, it shows that it is a base.

(vi) The liquid in test tube C does not turns the colour of either blue litmus or red litmus thus is distilled water.

1 Step : Put blue litmus paper Test tube A Test tube B Test Tube C \[\Downarrow \] \[\Downarrow \] \[\Downarrow \] turns red remains blue remains blue \[\Downarrow \] \[\Downarrow \] \[\Downarrow \] \[\] \[\] 2 Step : Put red litmus paper (red turned by acid) Test tube B Test tube C \[\Downarrow \] \[\Downarrow \] turns blue remains red \[\Downarrow \] \[\Downarrow \] \[\] \[\]