How can I find molecular weights for specific substances?

Can you tell me the molecular weights of KHP and aspirin?
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First, you must look up the molecular formula for the compounds. The molecular formula of KHP (potassium hydrogen pthalate) is C8H5O4K, and the molecular formula of aspirin (acetylsalicylic acid) is C9H8O4.

The sum of atomic weights in the formula gives you the compound's molecular weight:
KHP, KC8H5O4aspirin, C9H8O4
8 carbons8×12.011 = 96.0889 carbons9×12.011 = 108.099
5 hydrogens5×1.00797 = 5.039858 hydrogens8×1.00797 = 8.06376
4 oxygens4×15.9994 = 63.99764 oxygens4×15.9994 = 63.9976
1 potassium1×39.102 = 39.102sum:180.160
sum:204.227

Author: Fred Senese senese@antoine.frostburg.edu



General Chemistry Online! How can I find molecular weights for specific substances?

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