Author: Charco
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How can enthalpy of formation values be used to calculate reaction enthalpy?
Friday, May 18th, 2007 Think about it this way… the reactants (left hand side) go on to make the products (right hand side) Imagine that this reaction proceeds VIA the elements in their standard states, (according to Hess’s law we can go any way we want providing that we get to the desired products) First…
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What is the structure of sulfur(IV) oxide?
SO2 seems to be a little confusing as there are several different descriptions circulating. Some books claim that it has an expanded octet, although there is no real evidence to support this. It can be simply described without octet expansion in that there are only 8 electrons around the central sulfur atom. On a simplistic…
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How is the volume measurement of hydrogen peroxide related to its molarity?
May 21st, 2007 Hydrogen peroxide decomposes according to the equation: 2H2O2 –> 2H2O + O2 If you start with 100 volume H2O2 then 1 dm3 of solution will release 100 dm3 oxygen (at RTP) This means that 1 litre of H2O2 solution releases 100/24 moles of oxygen and as 2 moles of H2O2 decompose to…
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How can I test for an alcohol?
May 21st, 2007 To detect the presence of the OH group regardless there are several simple tests that can be done, however they all have the disadvantage of interference by water. A small piece of sodium metal can be placed in the alcohol and a steady stream of hydrogen bubbles gives a positive indication. Remember…
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What actually happens when a liquid boils?
May 21st, 2007 All liquids contain particles in which the energy distribution is governed by the laws of statistics. This energy distribution may be plotted as a curve, called the Maxwell Boltzmann graph that shows some particles with very little energy, some with large amounts of energy and the bulk of the particles with energy…
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How does electrolysis work?
May 26th, 2007 There are several misconceptions about electrolysis, such as the idea that electricity flows across the electrolysis cell. The conditions required for electrolysis are an electrolyte with ions that are free to move. They may be in solution or in the form of a molten salt. There must then be an electrical potential…
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What does oxidation state actually mean?
May 31st, 2007 The term oxidation state is a convenient way of describing the effective condition of an atom in a compound in terms of the charge that it would have if it were ionic. It is not intended to suggest that atoms have a specific charge, but it is a useful way of describing…
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Why do allotropes have different colours?
May 31st, 2007 Colour is caused by selective absorption of certain wavelengths and reflection of the rest. The most familiar example would be that of phosphorus, which has three allotropes each of which have a different colour; white, red, and black, and several variations within these three basic forms. The structure of the red form…
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What is water of crystallisation?
May 31st, 2007 Water of crystallisation is the term given to the molecules of water that are used to build up a crystal lattice in some ionic compounds. In copper(II) sulfate the blue crystals would be impossible without using water molecules to act as ’scaffolding’ within the structure CuSO4.5H2O. When this is heated the water…
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What is hardness in water
June 14th, 2007 Hardness is a term to describe water that doesn’t allow soaping action, in other words no bubbles (lather) and no cleaning. The term ’soaping action’ refers to the formation of micelles by negative ions joined to long carbon chains that dissolve in the fat or grease leaving the negative charges outside the micelle…