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Effect of Sodium Hydrogen Carbonate Concentration on the Rate of Photosynthesis

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Effect of Sodium Hydrogen Carbonate Concentration on the Rate of Photosynthesis Method Firstly I will attach a capillary tube to the nozzle of end of a 20cm3 syringe by means of rubber tubing. I shall push the end of the capillary tube to the tip of the nozzle of the syringe, ensuring that the rubber tubing provides an airtight seal. Using razor blade I will cut three sections of the Elodea stem and after removing the plunger I shall place the cuttings into the nozzle. I will also make certain that the cut ends of the Elodea are facing upwards away from the nozzle end. After this is prepared I can then place the different concentrations of sodium hydrogen carbonate solutions into the barrel. The solutions that are to be used are 0.0100, 0.0125, 0.0166, 0.0250, 0.0500, 0.1000 mol dm-3. To do this I will place my finger over the open end of the capillary tube. Then slowly I will pour one of the concentrations of sodium hydrogen carbonate into the barrel. I will add the solution until the Elodea is covered to the 20cm3 marking. I will then invert the apparatus and slowly push the plunger to push out all the air bubbles from the capillary tube and also makes certain no air is trapped between the plunger and solution in the barrel. ...read more.


In the concentration of 0.0100 mol dm-3 the largest movement of the meniscus was three millimetres showing that enough carbon dioxide is reaching the Elodea. In the concentration of 0.0125 mol dm-3 the movement of the meniscus has increased but only buy a few millimetres. There is a steady increase till 0.0250 mol dm-3. In the concentration of 0.0250 mol dm-3 between the 3 minutes from 3 to 6 there was a significant movement in the meniscus of 15 millimetres. Therefore showing the carbon dioxide level reaching the Elodea must have declined a great deal to force the Elodea to increase the carbon dioxide intake. Though after this, the amount the meniscus moves goes back in concordance with the rest of the results. This may show an anomalous result but after calculating the average the results fall back into concordance. In the concentration of 0.0500 mol dm-3 a significant increase can be seen of the movement of the meniscus. The movement of the meniscus in the first 3 minutes is 9 millimetres and in the next three minutes the movement of the meniscus increase to 18 millimetres. There is also a significant increase in the last 3 minutes for 15 millimetres. In the last concentration tested 0.1000 mol dm-3 the results table show that here is the largest movement of the meniscus. ...read more.


Many improvements can be carried out during the procedure to reduce the degree of inaccuracy in the results obtained. A more secure connection between the capillary tube and the nozzle of the syringe can be made. Switching the lamp off before each experiment could would prevent the temperature increasing and therefore the enzymes themselves working faster. When pulling the plunger back ensuring there were no air bubbles or spaces in the barrel or capillary tube. Using a more concentrations of sodium hydrogen carbonate would give a more accurate set of results. And also taking more replicates and repeats would enable me to see if my results are reliable. Using a more convenient apparatus than a clamp and boss to hold the capillary tube and would also make certain that the lamp was 8cm away from the Elodea. Measuring the meniscus with a more accurate instrument than a ruler would give more accurate results. All these factors should be considered so the experiment can be improved if I was to do a similar or the same experiment again. From the analysis and evaluation it can be seen that limitation and errors with the method have caused the results to be unreliable. However I can also conclude that the results have been successful to a degree as they did show the correct trends and patterns ...read more.

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