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what is simple formula and molecular formula?
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I've never heard the expression "simple formula" used before but I presume you are talking about the difference between the empirical formula and the molecular formula. The empirical formula of a compound is the one with the lowest molar ratio of each atom in the molecule.
As an example, most carbohydrates have the empirical formula of CH2O. All molecular formulas have a single factor multiplied by the ratios of 1:2:1 for C:H:O.
Ribose is a 5 carbon sugar and has a molecular formula of 5*(CH2O) = C5H10O5.
Glucose is a 6 carbon sugar and has a molecular formula of 6*(CH2O) = C6H12O6.
Comments
To clarify, simple sugars have the empirical formula of CH2O.
polysaccharides (e.g., sucrose, starch) are formed by linking simple sugars together, but H2O is lost each time that happens (sucrose is composed of two simple sugars, with a link between them, so there is one H2O less than expected)
- Dick B. 2/10/2013To further clarify this clarification, starch is a polymer of glucose and has a variable molecular formula that is an integer multiple of its empirical formula: (C6H10O5)n. Where n is the number of glucose molecules that have been incorporated into the polymer. There are examples of other monosaccharides or "simple sugars" like deoxyribose and fucose that do not follow the CH2O empirical formula as well. My intention was not to get involved in a lengthy discussion of sugars but only to use two examples to illustrate a point about your question regarding empirical and molecular formulas.
- Michael B. 2/10/2013