9. Which of the following solvents is used in normal phase elution in HPLC? a) Ethanol: Water b) Hexane c) Acetonitrile CH;CN d) Methanol 11. Analyte that are extremely Hydrophobic (or) incompatible with water, a mobile phase that contains no water is used. The separation is termed as : a. Reversed phase chromatography b. Normal phase chromatography c. Non- aqueous Reversed phase chromatography d. Aqueous Normal phase chromatography

Portfolio V (6-10)

Your measurements indicate that the concentration at valve V7 is 2.04 ppm, while the concentration at thetop of the column is 3.06 ppm. Calculate the normalized concentration at V7. Report using four decimalfigures to an accuracy of ± 0.0001.

Insects do not have lungs as we do, nor do they breathe through their mouths. Instead, they have a system of tiny tubes, called tracheae, through which oxygen diffuses into their bodies. The tracheae begin at the surface of the insect's body and penetrate into the interior. Suppose that a tracheae is 1.34 mm long with a cross-sectional area of 2.46 x 10-9m2. The concentration of oxygen in the air outside the insect is 0.794 kg/m3, and the diffusion constant is 1.26 x 10-5 m2/s. If the mass per second of oxygen is diffusing through a trachea is 1.66 x 10-12 kg/s, then find the oxygen concentration at the interior end of the tube.