Almost! What is eliminated (removed) when an ester (or polyester) is formed from a carboxylic acid and an alcohol (polyol)? How many moles of this molecule are formed and eliminated to make the polyester, and what is the total weight of the substance eliminated?
Correct the weight of the polymer formed by the weight of the eliminated substance and redo your calculation.
Ok ! Water is produced and must be removed (Le chatellier ). But how to use this information (amount of water produced/removed) to calculate the OH number ?
He's already told you this. Use the weight of water removed to correct the weight of the polymer in your calculation.
Colin
Ok ! Water is produced and must be removed (Le chatellier ). But how to use this information (amount of water produced/removed) to calculate the OH number ?
Please keep in mind that you are only looking at the difference between acid groups and OH group. At start of the reaction nothing has reacted and your OH is 480 (and AV=424). Remove water and both will go down. Without losses and decomposition you will end up with your OH=56! regards Koos
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