One bottle contains NaOH solution, another contains dilute H2SO4 and the third contains NaCl solution. How can you tell what’s in a bottle with just litmus paper?
Answer: The solution was taken from each bottle and placed in three test tubes separately. The litmus paper was cut into three pieces and placed into the solution in each test tube. The solution that turns the paper red is H2SO4. The solution that turns the paper blue is NaOH. The solution which will not change the colour of the paper is the NaCl solution.