Practice questions: nore moggnpolar A pigment solution contains compound A with

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Practice questions: nore moggnpolar A pigment solution contains compound A with 4 po You plan to separate these compounds using paper chromatography with a nonpolar solvent. Predict the location of the two bands relative to the solvent front. Explain your answer. 3. ups and compound B with 2 polarigroups. Land plants and many algae appear green, due to the chlorophyll stored in their chloroplasts However, the deep-ocean-dwelling red algae, as their name suggests, these red algae range in color from a darkish pink to red to dark purple, to almost black. These varied red colors are attributed to the photosynthetic pigment phycoerythrin. What color and wavelengths do you think phycoerythrin absorbs? 4. Suppose a farmer decides to build a greenhouse using green-tinted glass instead of clear glass. Why is this a bad idea? 5. 6. A scientist wants to determine the best light wavelength for growing plants. He grows plants in four groups as shown on the table below. What is wrong with the design of his experiment? Be specific. Light wavelength CO2 Level Light Group A (10 plants) B (10 plants) C (10 plants) D (10 plants) 400 nm 500 nm 600 nm 700 nm Intensity 30% 80% 50% 20% 6

Explanation / Answer

3. Chromatography is a technique for seperating mixtures based on the speed they migrate. Polarity has a huge effect on this. The larger the charge difference the more polar the molecule is and hence compound A has 4 polar groups it is more polar and compound with 2 polar groups is less polar and can be non polar. More polar molecules spends its time in the polar solvents whereas non-polar groups spends it time in non polar solvents. So in the paper chromatography either polar or non polar solvents are used and these compounds A and B migrate to some extent with the solvent front. Here non polar solvent is used and the polar components do not move or migrate with the non polar solvent and rate of moving is slow but the compound B with only 2 polar groups migrate fast to the solvent front. So the location of compound B would be near the solvent front but location of compound A appears at the initial point.

4. Phycoerythrin is usually a red protein pigment present in red algae. This absorbs blue,green and yellow lights and their wavelengths ranges of these are between 450 to 590. Blue 450 and yellow 590. So the wavelengths of phycoerythrin in the visible light is measured at 495,545 or 566nm. This depends on the chromophore bound to it.

5. Glass is the important material for green houses. Choosing the type of glass is also very important. Green glass absrobs green light or reflects it and that is why it appears green. So this reduces the light intensity inside the green houses and plants cannot absorb sufficient amount of light and it is not useful to the plants. Whereas a clear glass absorbs more amount of light which is utilized by the plants and this light is trapped by the plants and do not allow the heat out. So using a green tinted glass is a bad idea.

6. Plants use chlorophyll which reflects green light. But they absorb red and blue lights for their growth and less amounts of green and yellow. So they utilize the wavelength of blue that is 500nm at maximum and red light with 600nm in the table. In artificial lightning plants need highest light intensities. And the light intensity at 500nm and 600nm is greater ie 80% and 50% and also the CO2 level is higher than in Groups A and D. So these are favourable conditions for the plants to grow and in this design of experiment the duration of exposure to light is very important. The exposure should not be too much and not too less. It must be atleast 12hours in a day for efficient growth. And providing light too long might damage the plant.

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