Author: Charco
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Latest additions to Colourful Solutions – Structural types self-test
Here’s a new organic self-test on structural types.
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What is the difference between bond enthalpy and bond dissociation enthalpy?
The bond energy term is the energy actually required to break a bond, or rather a mole of these bonds. The fragments that you produce depend on what the actual bond is holding together. There are two terms that are used: 1. Bond enthalpy – this is the average of a bond of a certain…
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How does atomic absorption work?
To understand atomic absorption it is necessary to take a look at some of the concepts involving the nature of light itself. Light is just a form of electromagnetic radiation. The term electromagnetic radiation refers to the propagation of energy through a medium (or a vacuum) in the form of oscillations of an electrical nature with…
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How does the iodine clock reaction work?
The iodine clock reaction times how long it takes for a fixed amount of thiosulphate ions to be used up, i.e. the time taken for the iodide ions to reach a fixed number of moles produced in the reaction between potassium iodide and an oxidising agent (usually hydrogen peroxide, or sodium peroxodisulphate). The system is…
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Which factors determine the percentage yield in a laboratory preparation?
Experimental preparations of compounds usually follow the standard methodology, i.e. 1. reaction 2. work-up 3. purification The theoretical yield can be simply calculated froma knowledge of the stoichiometry of the reaction(s) involved in the preparation. The final percentage yield is calculated from actual yield/theoretical yield x 100% For example In the preparation of nitrobenzene by…
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What is the molecular formula of sulfur?
The formula of the elements is best left to the simplest possible form, except in the case of the gases and the halogens, that are shown as diatomic molecules by tradition. The remaining elements are simply expressed as a single atoms, although it must be emphasised that elements, or rather the atoms of elements, do not…
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How does copper react with nitric acid?
Copper is an unreactive metal and doesn’t react in normal circumstances with dilute acids. However it does react with nitric acid. Why is this? Nitric acid is an oxidising agent and the reaction is not the usual acid + metal reaction. The products are oxides of nitrogen instead of hydrogen. The actual nitrogen oxide formed…
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Which factors contribute to the boiling point of ethanoic acid?
Boiling points are a function of the intermolecular forces. The ethanoic acid dimer has an effective RMM = 120. This means that considerable Van der Waals force would be expected between particles. Compare with a totally non-polar molecule with a similar relative mass such as decane. The boiling point of decane is 174ºC. Were ethanoic…
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Why can hydrogen peroxide act as both an oxidising agent and a reducing agent?
Hydrogen peroxide has the ability to gain or lose electrons, as its oxygen atoms are in the -1 oxidation state. By gaining electrons they can go to the -2 oxidation state, and by losing electrons they can go to the zero oxidation state (the element) When someting acts as an oxidising agent is gains electrons…
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Why do we study kinetics of reactions?
Original post: Friday, May 18th, 2007 The study of kinetics is to find out the things that affect how fast reactions occur and then ultimately to explain the actual mechanics of the process (what actually happens and in which order) On the basic level, simply observation shows us that changing the concentration of reactants affects…