1 By convention a normal lens on a 35mm film camera (and thus a full-frame EOS digital SLR) has a focal length of 50mm or so. 2  A lens with a focal length of 35mm is considered ânormalâ for a cropped-frame EF-S camera.
Aspirin. One of the best known aromatic acetates is acetylsalicylic acid, or aspirin, which is prepared by the esterification of the phenolic hydroxyl group of salicylic acid. Aspirin possesses a number of properties that make it the most often recommended drug.
Therefore, aspirin (or acetylsalicylic acid) contains: - aromatic ring - carboxylic acid group - ester group and can be regarded as an acid (i.e. acetylsalicylic acid) or the acetate ester of salicylic acid :-) so aspirin is (if choosing from your options): - not an alkene, nor a ketone, nor an alcohol.