List three ways that pH can be measured in the laboratory, and briefly describe how each method works
1. Indicator paper. This consists of strips of paper impregnated with indicator solution and dried. The paper turns a different color depending upon the pH of the solution. This method is very fast and simple. But it is too coarse. We can use this method in organic synthesis or different experiments for the control pH. 2. Acid–base titration. This method A solution of known concentration (titrant) is added dropwise to the test solution. When they are mixed a chemical reaction takes place. The equivalence point - the moment when the titrant is exactly enough to complete the reaction - is fixed by the indicator. Further, knowing the concentration and amount of added titrant solution, the acidity of the solution is calculated. This method is more precise than indicator paper, 3. Potentiometric method. This method is much more accurate, but it requires special equipment laboratory instruments - pH-meters. Potentiometric method based on measurement of the EMF of the electrode system consisting of the indicator electrode and the reference electrode. First, measure the EMF of several buffers to set the value of pH, define the parameters Eo and Ɵ in the equation of dependence E = Eo - ƟpH, and then measure the EMF of the test solution. Having calculated the dependence of its pH.