pH

  An aqueous solution can be acidic, neutral and alkaline, and this depends on the difference hydrogen ion and hydroxide ion concentrations in the solution. Hydrogen ion concentration can be expressed by pH value.

how to calculate pH value

  Generally, the higher the hydrogen ion concentration, the lower is the pH value.

  An acidic solution has a pH value less than 7; a neutral solution has a pH value of exactly 7; an alkaline solution has a pH value greater than 7.

pH paper gives different color at different pH values, so compare the color of the pH paper (with few drops of solution to be tested) with a pH chart or pH bar to find out the pH value

  To measure the pH of a solution, universal indicator (pH paper), a pH meter and a data-logger with pH sensor can be used.

Indicator

  An acid-base indicator is a special dye whose color depends on the pH of a solution. Thus, it can tell the pH value of a solution with a pH scale. There are three commonly used indicators: methyl orange, litmus and phenolphthalein.

different colors of acid-base indicators in different pH ranges