Interactive Chemistry Worksheets for Students
Lemons are sour because they each contain a chemical called citric acid.
Citric acid is a weak organic acid found in citrus fruits like grapefruit, oranges, limes and lemons.
In its pure form citric acid is a white crystalline solid and is sour to taste like all food acids. It is sold as a food addictive for cooking and can be found in most supermarkets.
The IUPAC or systematic name for citric acid is 2-hydroxypropane-1,2,3-tricarboxylic acid. The molecular formula of citric acid is C6H8O7
The chemical formula for citric acid is best shown by a diagram of its complete structural formula. This shows how the atoms are arranged in the molecule
Citric acid has three carboxyl or - COOH groups and is triprotic in nature. It weakly dissociates in water producing a weak acidic solution.
Citric acid(aq) ==> citrate ions + H+(aq)
92.1% 7.9% 7.9%
The pH of a 0.1 M solution of citric acid is 2.1