Archive for April 2013
CHM456 labs. Questions. – UPDATED.
Answer the questions briefly, yet informatively.
Week 1. Experiment: Acid-Base Extraction
See lab manual for first set of Q’s… then,
6) What was the purpose of adding NaOH?
7) What was the purpose of adding HCl?
8) Why was ether used in the extraction and not methanol?
9) Would the procedure work for methanoic acid? Give reasons.
Week 2. Experiment: Preparation of 4-methylcyclohexene from dehydration of 4-methylcyclohexanol
See lab manual (which refers to Q’s in Pavia)
a) What is the function of H2SO4?
b) Suggest two reasons why conc acid is used and not dilute H2SO4
c) Why is the c.H2SO4 added slowly and under cooling?
d) Sometimes the bromo alkane layer is at the top and sometimes it is on the bottom. Why?
e) Why should the trying agent (anhydrous CaCl2 or anhydrous Na2SO4 or anhydrous NaHSO4) removed before distillation
f) We do NOT distil to dryness. Why?