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Description
Programme examines the combination of boron trifluoride and ammonia, a Lewis acid-base reaction and the thermodynamic stability of the Group 5 hydrides.
Programme examines the combination of boron trifluoride and ammonia, a Lewis acid-base reaction and the thermodynamic stability of the Group 5 hydrides.
| Item code: | S25-; 10 |
|---|---|
| First transmission date: | 03-06-1972 |
| Published: | 1972 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:34 |
| + Show more... | |
| Producer: | David Jackson |
| Contributors: | Len Haynes; David Johnson; Joan Mason; David Strange |
| Publisher: | BBC Open University |
| Keyword(s): | Ammonia and boron trifluoride; Combustion of phosphine; Decomposition; Decomposition of arsine; Formation of the adduct; Hydrides; Infra-red spectrum; Molecular geometry; Vacuum system |
| Footage description: | Len Haynes with a large periodic table introduces the programme. Joan Mason in the laboratory demonstrates the formation of covalent bonds in a Lewis acidbase reaction. Commentary by Joan Mason. She explains the experimental techniques used and gives details of the reaction. The experiment is conducted in a vacuum system. Joan Mason, before examining the infra-red spectra of the two gases and the adduct from the above reaction, reviews their bending and stretching vibrations with the aid of molecular models. She then examines their I/R spectra. Mason then demonstrates the reaction process with molecular models. She shows that the line pair of nitrogen in NH₃, becomes the B-N bond pair of electrons and that BF₃ becomes tetrahedral. She then points out the now totally symmetric stretching vibration on the I/R spectrum. Len Haynes with a periodic table points out the elements of Group 5. He poses the question 'Is there a trend of stability among the hydrides of this group?' David Johnson uses a board to write out the equation for the decomposition of NH₃. He includes the standard free energy change, David Strange prepares arsine, the hydride of arsenic, in the laboratory and then tests for it. Commentary is by Johnson. Johnson writes out the equation for the decomposition of arsine together with the standard free energy change. David Strange prepares phosphene gas. This is seen to ignite on contact with the air. Johnson writes out the equation for the decomposition of phosphene together with the standard free energy change. He compares the thermodynanic stability with those of ammonia and arsine. Johnson writes out the equations for the decomposition of the rest of the Group 5 hydrides together with their standard free energy changes. A smooth trend of decreasing thermodynamic stability down the group can be seen. Johnson uses molecular models and the board showing the decomposition equations to examine the bonds formed and broken during decomposition at molecular level. |
| Master spool number: | 6LT/70291 |
| Production number: | 00521_2165 |
| Videofinder number: | 1778 |
| Available to public: | no |
