1) The mass of caffeine in a particular coffee drink was determined by high-performance liquid chromatography (HPLC). The calibration curve produced from running standard solutions of caffeine through an HPLC column is shown below.

A 5.0 mL aliquot of the coffee drink was diluted to 50.0 mL with de-ionised water. A sample of the diluted coffee drink was run through the HPLC column under identical conditions to those used to obtain the calibration curve. The peak area obtained for this diluted sample was 2400 arbitrary units.

The HPLC column used has a non-polar stationary phase. The most suitable solvent for determining the concentration of caffeine in the sample is
A. carbon tetrachloride, CCl₄
B. methanol, CH₃OH
C. octanol, C₈H₁₇OH
D. hexane, C₆H₁₄

Solution

2) The mass of caffeine, in grams, in 350 mL of the undiluted coffee drink is closest to
A. 0.014
B. 0.070
C. 0.14
D. 0.40

Solution