The method and the results are on the organic nomenclature lab. Do the analysis yourself first, then check the answers below.
Quick answer: IUPAC nomenclature names an organic compound from its longest carbon chain, its functional group and its substituents, with numbers giving their positions. These answers go with the Chemistry 11-12 lab on organic nomenclature: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
Here are the organic nomenclature lab answers for chemistry grades 11-12: graph, calculations, uncertainties and conclusion. First do the lab yourself, then compare, and go back to the lesson if needed.
These model answers use the sample data in the table. Your own angles will differ a little, but the rotation should rise in a straight line with concentration and the unknown should fall between the standards.
Level: Chemistry grades 11-12 (A Level · IB · Class 11-12) · Curriculum: IB S3.2
Rotation is proportional to length, so 2.0 dm gives 2 × 19° = 38°.
Question 5 Enantiomers
Each enantiomer rotates light by the same angle in opposite directions. In a racemic mixture the rotations cancel exactly, giving zero net rotation.
Question 6 Uncertainty
Percentage uncertainty = (1 ÷ 7) × 100 = 14 %, large because the angle is small.
Question 7 Improvement
Use a longer tube (for example 20 cm) to increase the angles, and read the angle with a finer scale or mean of several readings. Keep the lamp and filters fixed between tests.
