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The whole of this programme is devoted to the remarkable properties of fluorine and its compounds. First the reactions of fluorine gas with uranium oxide, xenon, platinum, iron, sulphur, carbon, io...dine, and hydrogen are demonstrated. We see the violent reactions with many elements, and the slow growth of xenon difluoride crystals (with time-lapse photography). Then the problem of isolating fluorine is discussed and how, in 1866, it was finally solved by the French Chemist, Henri Moissan. The special properties of fluorine and their effect on fluorine compounds are discussed in the remainder of the programme. These properties; 1. The small size of fluorine; 2. The relative strengths of the X-F and F-F bonds; 3. The high oxidising power; 4. The low polarisability; 5. The high electronegativety, interrelate and help us to understand the extremes in fluorine chemistry, why, for example, some fluorine compounds are very reactive and others quite inert. Thus uranium hexafluoride, a reactive solid is compared with sulphur hexafluoride, a relatively inert gas. The inert qualities of sulphur hexafluoride are contrasted with the reactivity of the gaseous tetrafluoride. Other extreme properties are illustrated in the programme. The volatility of uranium hexafluoride, the acidity of trifluoracetic acid, and, those properties which make polytetrafluoroethylene such a remarkable polymer, are discussed.
Metadata describing this Open University video programme
Item code: S25-; 11
First transmission date: 17-06-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:23:55
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Publisher: BBC Open University
Keyword(s): Electronegativity; Extremes in fluorine chemistry; Fluorine reactions; Henri Moissan 1886; Isolation; Oxidising power; Polarisability; Size of fluorine; Strength of X-F and F-F bonds; Xenon difluoride crystals
Footage description: Len Haynes introduces the programme. A series of film shots show fluorine reacting with various substances. Commentary by Len Haynes. With Uranium oxide, with Xenon, with Platinum, with steel wool, with roll sulphur, with charcoal, with iodine crystals, with some IF-, with hydrogen in a balloon. Len Haynes introduces the sequence on preparation of fluorine. Joan Mason discusses the history of the search for a process to separate fluorine up to Henry Moissan's discovery in 1886. Shots of portraits of Davy, Ampere, Faraday, Moissan, old chemistry labs and equipment. Mason in her commentary explains the difficulties which were encountered and the processes which were used. Haynes briefly explains the modern method for separating fluorine. He then demonstrates an interesting property of UF₆ by placing a test tube of UF₆ in a basin of warm water. The UF₆ sublimes without melting. Joan Mason explains why fluorides are so highly volatile by looking at the forces between molecules which cause them to condense. She uses molecular models and diagrams to aid her discussion. Len Haynes examines the properties of UF₆ He explains how the compound is produced and the problems involved. Haynes demonstrates some of these properties. He exposes UF₆ to moist air (fumes form) and then induces a violent reaction in water. Len Haynes demonstrates the relative reactivities of SF₄ and SF₆. Joan Mason examines the reasons why some fluoride are quite inert. She uses ball molecular models and charts to aid her discussion. Mason puts forward the steric hypothesis and arguments in its favour. Len Haynes discusses some of the distinctive properties of fluorine. Size, bond strengths, oxidising power and electro negativity are all covered. The extreme electronegativity of fluorine is demonstrated. A pH meter is used to check the acidity of acetic acid and then trifluoroacetic acid. Joan Mason with a chart showing acid dissociation constants for acetic acid and its fluoro-derivatives. She then looks at an infrared spectrograph of a fluoro-organic compound which shows an interesting consequence of the electronegativity of fluorine. Len Haynes discusses the properties of the fluorine compound PTFE. He then examines some of the uses of PTFE. Joan Mason joins in the discussion. Molecular models, charts and still shots of applications are shown. Len Haynes sums up.
Master spool number: 6LT/70470
Production number: 00521_2198
Videofinder number: 1779
Available to public: no