54 East Extended Essays 2015
GURURAJ, ANANT
LEE, DONGKEUN
LEONG, BRIAN
The chosen research question for this essay is “How do the concentration, pH and Temperature of a Luminol reaction mixture affect the peak illumination and duration of its chemiluminescence?”. This topic was chosen because of Chemiluminescence’s known applications in forensic and pharmaceutical chemistry. By varying the Concentration, pH and Temperature of the reaction mixture, I hope to ascertain the conditions at which the light released during chemiluminescent reactions is most intense and the duration of the observable chemiluminescence is the longest.
The research question of this essay is to what extent the adsorption of heavy metal ions of zeolites can be determined as measured by colorimetric analysis of zeolite filtrates. It investigates the adsorption capability of both homemade and commercial zeolite A by monitoring the color change of zeolite filtrate using a colorimeter. Homemade zeolite A was synthesized to see the difference in adsorption capability compared to zeolite A, and sodium metasilicate, sodium aluminate with sodium hydroxide were prepared for Zeolite A synthesis. The solution was heated to 100˚C and cooled for crystallization, and approx. 50g of zeolite were obtained. Colorimeter was used to measure the reduction in solution light absorbency. As it is easier to quantify the data, Cu2+, Co2+, and Ni2+ were selected. Moreover, concentration of each heavy metal solution was varied to create a calibration curve to indicate unknown concentration of a corresponding light absorbance. An experiment was conducted to determine the saturation point of homemade zeolite A compared to commercial one. Heavy metal ion solutions were prepared in different concentrations varying from 0.10 to 0.60 moldm-3, and 10ml of each concentration were put with zeolite powder for an hour. Then the light absorbency of the filtrate was measured via colorimeter. The result suggested that homemade zeolites show similar adsorption capability to commercial zeolite A. The adsorption of heavy metal ions increased from Ni2+<Co2+<Cu2+. Abnormalities in the data trend suggest inconsistency in homemade zeolite structure and irregular pore size. It also suggests that mass-tocharge ratio of heavy metals also affect adsorption, the smaller the value, the less likely it will be adsorbed. The results conclude that colorimeter can be a viable method to measure zeolite adsorption capability, yet it some issues with the validity of the calibration curve as Beer-Lambert law tends to work better in lower concentrations.
This essay investigates how observed rotation can be used to determine the fructose/glucose ratio in different types of honeys. Honey is a supersaturated solution primarily composed of glucose and fructose, which rotate plane-polarized light in opposite directions and different magnitudes. The amounts of glucose and fructose vary with the source of nectar.
Luminol can exhibit chemiluminescence with different combinations of chemicals. Before the aforementioned factors were varied, three such combinations were tested. The combination of chemicals decided upon for experimentation consisted of Luminol, Sodium Hydroxide (Luminol Solution) and Sodium Hypochlorite (Oxidising Solution) as it produced fairly long-lasting and bright light. To vary the concentration and pH of the Luminol solution, different masses of Luminol and Sodium Hydroxide respectively were dissolved. To vary the temperature, the Luminol solution was placed in hot water baths and an ice bath (to lower temperature) before the reaction took place. The reaction was carried out in a 1 dm3 beaker when the Luminol and Oxidising Solutions were mixed. A light sensor connected to Logger Pro was used to gather data involving light released. The conclusion drawn was that the peak illumination is highest between pH 11 and pH 13 with a high concentration of Luminol and at as low a temperature as possible (approximately 11ºC was achieved with the ice bath). pH had the greatest effect on the peak illumination and temperature had the greatest effect on the duration of the observable chemiluminescence. At these conditions, the pH and concentration maximise the peak illumination and the temperature slows down the reaction, prolonging the chemiluminescence.
Solutions of five unifloral honeys: manuka, eucalyptus, honeydew, wild dandelion and blackberry were prepared in distilled water at a concentration of 0.10gcm-3. Moisture content in honey was considered when preparing solutions. The extinction points of each solution were measured using a polarimeter with 5 trials per concentration and subtracted from the extinction point of distilled water to find the observed rotation. The total sugar concentration was calculated from the nutritional information on the honey. By making the assumption that fructose and glucose are the only optically active compounds in honey, two equations for the concentrations of fructose and glucose were obtained. This allowed a formula for the fructose/glucose ratio in terms of sugar concentration and specific rotation to be derived. After data processing, it was found that eucalyptus honey contained the highest fructose/glucose ratio at 7.17, followed by manuka at 1.43, blackberry at 0.83, wild dandelion at 0.40 and honeydew at 0.27. Further avenues of investigation include grouping honeys according to their production location to see if it has any effect on the fructose/glucose ratio, investigating the effect of mutarotation on optical activity, using gel filtration chromatography instead of polarimetry to analyze the amounts of each sugar in different honeys and examining the effect of adding high-fructose corn syrup to honey on its specific rotation.