Chemistry Extended Essay - Viscosity of Xanthan Gum solutions

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How does the introduction of xanthan gum into a solution and the resulting increased viscosity affect the rates of reactions occurring within that solution?

Andrew Pelly



- Chemistry -

How does the introduction of xanthan gum into a solution and the resulting increased viscosity affect the rates of reactions occurring within that solution?

Word Count: 3731


IB NUMBER 000834 027


SECTION        TITLE                                                                PAGE

Abstract        2

  1. Introduction        3
  2. Research question        4
  3. Background information        4
  1. Xanthan gum in solution        4

  2. Electrolytic refinement        5
  3. Na-H2O ionisation reactions        6
  1. Method        6
  1. Viscosity measurements        6
  2. Rate of reaction measurement: electrolytic refinement        7
  3. Rate of reaction measurement: neutralisation reactions        7
  1. Data        8
  1. Relationship between xanthan gum concentrations and time                  taken for burette to empty, in order to model viscosity        8        
  2. Comparison of mass change of the cathode in an electrolytic       purification reaction involving a copper anode and a copper             cathode in a copper sulphate solution         9
  3. Peak temperatures achieved during Na/H2O ionisation reaction        11
  1. Analysis        12
  1. The homogeneity assumption        12
  2. Sodium and water reaction        12
  3. Hydrogen bonding in water        13
  1. Conclusion        15
  1. Xanthan gum solution viscosity testing        15
  2. Electrolytic refinement testing        15
  3. Na/H2O ionisation reaction        15

Appendix        16

  1. Bibliography        16


In this essay, I researched the question “How does the introduction of xanthan gum into a solution and the resulting increased viscosity affect the rates of reactions occurring within that solution?

Xanthan gum is a standard food additive used as thickening agent. It is very stable and only reacts at extreme pH and temperature values. In the experiments described in this essay, it was used as it is in food, as a thickener and the effect of the increased solution viscosity on the rates of oxidation and reduction was measured in two different experiments. The first was the electrolytic refinement of copper, electrolysed with an external power source in copper sulphate solutions, and the second was the ionisation of solid sodium in water.

The mass graphs for the copper anode and cathode in the electrolytic refinement reaction indicate that as xanthan gum concentration increased, the rate of reaction, and subsequently the mass change of the anode and cathode, was reduced. Other factors were gradually eliminated to establish that the viscosity caused a measurable amount of the reduction in reaction rate. 

The temperature graphs for the sodium ionisation occurring in water indicated that the sodium reached a lower peak temperature when the concentration gradient of xanthan gum within the solution was increased. Factors such as Fick’s first law were taken into account to establish that the increased viscosity and pseudoplasticity of the solution played a significant role in reducing the reaction rate and therefore also the peak temperatures of the sodium ionisation reactions.

Word Count: 253

1.        Introduction

Coal cutting seems like the most mundane job on the planet. However, with global demand for electricity ever higher, new coal burning power plants are opening at an extraordinary rate. Men who work as coal cutters process the carbon taken from the ground and make regular sized lumps of coal. The coal is then burnt in a power plant and used to heat water, create steam and drive turbines. If the coal cutters do not cut the coal small enough, the coal will have a reduced surface area relative to mass and burn too slowly to produce large amounts of energy. However, if they cut the coal into too small pieces the increased surface area will cause a much faster release of heat, and could cause an explosion at the power plant. Optimizing the rate at which the reaction between coal and air occurs is critical to producing the most efficient energy for our planet. With this in mind, I investigated a method for controlling rates of reaction.

Having experienced first-hand the importance of controlling rates of reaction in liquids during my practical work, I decided to focus my investigation on assessing the viability of varying viscosity as a method for controlling rates of reaction. Collision theory states that in order for a reaction to occur, the reactant molecules must have enough kinetic energy to bring about the reaction. There are already several methods for reducing the kinetic energy of molecules in solution, the simplest method being decreasing the temperature of the solution. I chose to test the effect of different levels of viscosity of a solution on the molecular kinetics of a reaction. I selected xanthan gum as a thickening agent.

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Xanthan gum (C35H49O29) is a long chain polysaccharide derived from the digestion of corn sugar by the bacteria Xanthomonas campestris. It is commonly used as a thickener and stabiliser in food products, from salad dressings to gluten-free bread. It is readily soluble in water, forming highly viscous gels even at low concentrations. It is also a very stable compound that does not spontaneously react over a wide pH range or with any salts. The viscosity of xanthan gum solutions is almost unchanged even when the temperature is raised; allowing comparison of reactions over a wider range of temperatures then would otherwise ...

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