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Chemistry 125: Lecture 20 Rise of the Atomic Theory (1790-1805) Elemental analysis was the technique for determining the composition of organic compounds.

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Presentation on theme: "Chemistry 125: Lecture 20 Rise of the Atomic Theory (1790-1805) Elemental analysis was the technique for determining the composition of organic compounds."— Presentation transcript:

1 Chemistry 125: Lecture 20 Rise of the Atomic Theory (1790-1805) Elemental analysis was the technique for determining the composition of organic compounds. Lavoisier's early combustion and fermentation experiments showed a new, though naïve, attitude toward handling experimental data. Dalton’s atomic theory was consistent with the empirical laws of definite, equivalent, and multiple proportions. The basis of our current notation and of precise analysis was established by Berzelius, but confusion about atomic weight multiples, which could have been clarified at the outset by accepting the suggestions of Avogadro and Gay-Lussac, would persist for more than half a century. Synchronize when the speaker finishes saying “…as far as their practical application in organic chemistry...” Synchrony can be adjusted by using the pause(||) and run(>) controls. For copyright notice see final page of this file

2 Elementary Treatise of Chemistry 1789 PRESENTED IN A NEW ORDER AND ACCORDING TO MODERN DISCOVERIES With Figures

3 Oxidation States Radical 1° "oxide" 2° "-ous" acid 3° "-ic" acid 4° "oxygenated -ic" acid

4 Elemental Analysis by Oil Combustion Air Supply Lamp Oil Supply H 2 O Collector CO 2 Collector

5 How to analyze a substance that will not burn cleanly? e.g. grape sugar Everyone knows how wine, cider and mead are made…

6 Plate X: Fermentation Apparatus H 2 O Absorption by CaCl 2 CO 2 Absorption by NaOH soln. any other Gas Foam catcher Sugar/Yeast/Water

7 I can consider the materials subjected to fermentation and the products of fermen- tation as an algebraic equation; and by in turn supposing each of the elements of this equation to be unknown, I can derive a value and thus correct experiment by calculation and calculation by experi- ment. I have often profited from this way of correcting the preliminary results of my experiments. Fermentation it can furnish a means of analyzing sugar Oxidation failed with air oxygen sulfuric acid mercuric oxide etc. because of incomplete combustion (charring)

8 Lavoisier’s Bookkeeping 72 grains = 1 gros 8 gros = 1 ounce = 28.35 g

9 Lavoisier’s Bookkeeping


11 Hydrogen Generator Red-hot Glass Tube Water 28 grains Carbon Water Water (less 85.7 grains) 144 cu. in. (100 grains) Carbonic Gas 380 cu. in. (13.7 grains) Flammable Gas Carbon + Water 28 gr. 85.7 gr. = Carbonic Gas + "Hydrogen" 100 gr. 13.7 gr. "I have thought it best to correct by calculation and to present the experiment in all its simplicity." 157 313 103 9.4 from 28 gr. C (modern theory) ……… ? + + = ! 1.38 g Trait é pp. 88-92

12 FactsIdeas Words Lavoisier Contributions Elements Conservation of Mass Oxidation Radical/Acid Salts Apparatus Quantitation Mass volume Substances Reactions Meaningful Names Element - Oxidation State - Salt Composition -ous, -ic, -ide, -ite, -ate Clarity

13 [Chemistry's] present progress, however, is so rapid, and the facts, under the modern doctrine, have assumed so happy an arrangement, that we have ground to hope, even in our own times, to see it approach near to the highest state of perfec- tion of which it is susceptible. Lack of Imagination

14 "Il ne leur a fallu qu’un moment pour faire tomber cette tête, et cent années peut-être ne suffiront pas pour en reproduire une semblable." "It took them only an instant to make this head fall, but a hundred years may not suffice to reproduce one like it." Lavoisier Guillotined May 8, 1794 Age 50 "The Republic has no need of geniuses.” But all of his equipment (including 80 pounds of mercury) was seized for The People.

15 Boyle Lavoisier √ √

16 John Dalton Why do gases of different density remain mixed rather than stratifying? amateur meteorologist 1801 Continental European scientists proposed that different gases attract one another.

17 "the atoms of one kind did not repel the atoms of another kind" Atom “Heat Envelope” Match  Repulsion Mismatch  Reduced Repulsion Substitutes homorepulsion for heteroattraction

18 Atoms Explain: Definite Proportions Equivalent Proportions Multiple Proportions Pure compounds always have the same weight ratio of their elements. If a parts of A react with b parts of B, and a parts of A react with c parts of C, … If two elements form several compounds, their weight ratios are related by simple factors. and d parts of D react with b parts of B, then d parts of D react with c parts of C.

19 Definite Proportions? Joseph Louis PROUST (1754-1826) Claude Louis B ERTHOLLET (1748-1822) NON!OUI ! metal alloys natural "organic" materials "chemicals" 

20 Multiple Proportions O/C 2.57 1.27 O/N 0.58 1.27 2.39 Oxides of Carbon%C%O 2872 4456 Carbonic Acid (1801) Carbonous Acid (1789) Oxides of Nitrogen%N%O 63.3036.70 44.0555.95 29.5070.50 Nitrous Oxide (1810) Nitrous Gas (1810) Nitric Acid (1810) [1] ~2 2.19 ~4 4.12 ~2 2.02 [1] Rel. integral values consistent with simple atomic ratios %err of (O/C) vs. modern -4 -5 -2 +11 %err of (O/N) vs. modern

21 Genealogy Top

22 Berzelius etc. √

23 Berzelius Jöns-Jakob BERZELIUS (1779-1848) Organic & Mineral Analysis Dualism (double decomposition) Electrolysis Notation for Composition Teaching & Writing Textbook (1808) 2000 compounds in 6 years! Good Atomic Weights for 50 elements!

24 Notation for Composition Alchemy Dalton Berzelius

25 Chemical Symbols of 1774 (Sweden) 1774 Symbols

26 “When only one combination of two bodies can be obtained, it must be pre- sumed to be a binary one, unless some other cause appear to the contrary.” Chemical Symbols of 1774 (Sweden) HO HN NO HC OC N 2 O NO 2 CO 2 CH 2 H N C O P S Mg Ca Na K Sr Ba Fe Zn Cu Pb Ag Pt Au Hg (Corresponding Berzelius Symbols) Dalton Notation (1808) NO 3 SO 3 SH 3 C 3 H “When four…one binary, two ternary, and one quarternary, &c. Latin (international) Analytical (NOT structural) Berzelius Notation (1811) Dalton’s Logic N 2 O NO 2 CO 2 CH 2 NO 3 SO 3 SH 3 C 3 H When three…a binary, and the other two ternary. ” “When two combinations are observed, they must be presumed to be a binary and a ternary…

27 Abbreviations: Dots denote O atoms = KO CrO 3 Superscripts denote numbers of atoms Benzoic should be H 10 C 14 O 3 (“acid” as anhydride) Didn’t catch on

28 Atomic Weights and Equivalents

29 Dalton’s Atomic Weights (1808) Weights 1 5 7 9 13 HCNOPSHCNOPS 2004 1 12 14 16 31 32 /1 /2 /3 /2 /3 /2 % err 9 16 5 12

30 Silicon Chloride SiCl T. Thomson SiCl 2 L. Gmelin SiCl 3 J. J. Berzelius SiCl 4 Wm. Odling ?

31 Joseph Louis Gay-Lussac (1809) Oxidation of Sugar, etc. with NaClO 3 Cleans up Lavoisier's Mass Balance 1.9989 volumes of hydrogen per 1.0000 volumes of oxygen Water gives 3.08163 volumes of hydrogen per 1 volume of nitrogen Ammonia gives Alternative to Dalton's Law of Greatest Simplicity 1804 - 7,016 m (record for 50 years) (1778-1850) Established that atmosphere composition is invariant with altitude.

32 End of Lecture 20 Oct. 22, 2008 Copyright © J. M. McBride 2009. Some rights reserved. Except for cited third-party materials, and those used by visiting speakers, all content is licensed under a Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0).Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0) Use of this content constitutes your acceptance of the noted license and the terms and conditions of use. Materials from Wikimedia Commons are denoted by the symbol. Third party materials may be subject to additional intellectual property notices, information, or restrictions. The following attribution may be used when reusing material that is not identified as third-party content: J. M. McBride, Chem 125. License: Creative Commons BY-NC-SA 3.0

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