The purpose of this lab is to determine the optimal concentration of NaCl
Sodium Chloride Water Peroxide Test tubes Potato puree (enzyme) 40 ml of beakers Pipette Dropper Test tube rack Tweezers Safety Goggles
Formula: C ₁V₁=C₂V₂ C ₁ = original concentration of the solution, before it gets watered down or diluted. C ₂ = final concentration of the solution, after dilution. V ₁ = volume about to be diluted V ₂ = final volume after dilution Ex 1: 4% NaCl Givens: C ₁ = 5% C ₂ = 4% V ₁ =? V ₂ =5ml (0.05)(v1)/0.05 = (0.04)(5) (0.05) (0.05) V ₁ = 4ml of NaCl 1ml of H ₂O
1. Find the calculations of the desired concentrations. Ex 4% NaCl. (4ml of NaCl and 1ml of H2O in 5ml solution.) 2. Label test tubes and beakers correctly for example Beaker A 5% NaCl, Test tube A, Beaker B 4% NaCl, Test tube B etc. 3. Pour 10ml of peroxide into the 6 test tubes 4. Take each concentration of NaCl and dilute it into each 40ml beaker, according to the calculations. 5. After placing each amount of NaCl in each 40ml beaker, add 1ml of potato puree into each solution. 6. Pour 6ml of potato puree into a 40ml beaker. 7. Using tweezers pick up a paper disk and drop it into Beaker A of diluted NaCl and potato puree solution.
7. Using tweezers take the paper disk out and allow it to dry for about 5 seconds. 8. Once dry place it in Test tube A of 10ml of peroxide. 9. Record the time it takes for the paper disk to rise up. 10. Repeat steps #7-10 for Beaker B-E and the 6ml of Potato puree. 11. Clean the equipment properly.
Percentage of NaCl (%)Time (minutes) to react 5 6:34 4 2:48 3 3:06 2 2:55 1 3:40 Control group 2:25
Due to our findings, it is determined that the paper disc in test tube # 4 rose up faster than the other paper disc. The test tube contained 10mL of H ₂ O ₂, but the paper disc was dipped into a beaker that was composed of 4ml of NaCl, 1ml of H ₂ O and 1ml of the potato puree. In this case, the beaker that held the solution of H ₂ O, NaCl and potato puree acted as an enzyme and hydrogen peroxide acted as the substrate of the catalase. A catalyst is a substance that lowers the activation energy required for a chemical reaction, which thereby increases the rate of reaction without being consumed in the process. The catalase is an enzyme, an organic catalyst. Hydrogen peroxide is the substrate for catalase. As the catalyst was breaking down the hydrogen peroxide into water and oxygen gas, the bubbles of oxygen collected underneath the filter and allowed it rise to the surface of the hydrogen peroxide.
The time it took for the filter to rise up is an indication of the rate of enzyme activity. The time it took the disk paper to rise was exceedingly high, since it depends on the concentration of the enzyme. Therefore the less concentrated the enzymes solutions are, the slower the rate of reaction. As for the other discs, the enzyme was not as concentrated as the 4% NaCl, it was perhaps due to the peroxide being at room temperature and also the fact that the rate at which an enzyme works is manipulated by many factors including pH. Group B (4% of NaCl), when compared to the control group, the paper disc rose faster since the solution only contained potato puree. This is also perhaps due to a greater concentration of the enzyme, which allowed the product to be produced promptly. Sources of errors would include not observing the time it took for the disc to rise up properly. Examples would include setting the timer and then leaving, once returned the disc has risen, the time to the disc rose would be inaccurate.
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Photos: Urinalysis Test. Retrieved October 16, 2011 from http://faculty.washington.edu/kepeter/119/images/urinalysis_tests.htm http://faculty.washington.edu/kepeter/119/images/urinalysis_tests.htm Close the loop initiative. How does it work? Retrieved October 16, 2011 from http://www.officeteam.co.uk/ot/closetheloop/how_does_it_work.htm http://www.officeteam.co.uk/ot/closetheloop/how_does_it_work.htm