Acids and Bases

In 1923, J.N. Bronstead and J.M. Lowry, working separately, proposed the definition that an acid is a substance that can donate a proton to another substance, and a base is a substance that can accept a proton from another substance. Strong acids would therefore increase the hydrogen ion concentration of a solution, and strong bases would increase the hydroxide concentration of a solution. The measurement of pH is a simplified way to express the hydrogen ion and hydroxide concentration of acids and bases. Using the pH scale, a solution with a pH of 7 is neutral, below 7 is acidic, and above 7 is basic. pH paper is one of the indicators used to measure the pH of solution; the paper changes color for known pH ranges. The pH paper, however, only determines relative ranges; a pH meter, an electronic instrument, is preferred for a more precise measurement of pH. This module simulates the measurement of pH for acids and bases with pH paper as the indicator. The calculated numerical value of pH is also displayed

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INSTRUCTIONS

1. Select an acid or base from the Acids & Bases list.

   HCl		hydrochloric acid		
   HF		hydrofluoric acid		
   HCN		hydrocyanic acid		
   HNO2		nitrous acid		
   HOC6H5		phenol			
   HOAc		acetic acid				
   NH3		ammonia			
   NaOH		sodium hydroxide
   (CH3)3N		trimethylamine
   (CH3)2NH2	dimethylamine
   (CH3)NH2	methylamine
   C6H5NH2		aniline		
   C5H5N		pyridine

2. Enter the concentration of the acid or the base in the Concentration box.
3. Click on the Dip button to measure the pH of the solution. Note: HOAc is a common shorthand symbolism for acetic acid, which has the formula HOOCCH₃. The acetate ion, OAc^-, is H₃CCOO^-.