1. La chimie est phun! Le pH P219 ‘Omnisciences 10’ Le pH est l’échelle de la puissance des ions d’hydrogène. Les scientifiques peuvent employer l’échelle de pH afin de mesurer l’acidité d’un produit chimique en solution aqueuse. Arrhenius , un chimiste suédois, a défini les acides et les bases en 1884.

2. From a very early age, Svante Arrhenius showed signs of a brilliant intellect. He taught himself to read at the age of three, and graduated from high school at age 17 as the youngest and brightest in his class. While attending university in Sweden, he began to study how electricity passed through solutions. From his work on the lowering of the freezing point of salt solutions, Arrhenius decided that the only way to explain the results was to assume that table salt, for example, broke up into two kinds of particles, sodium ions and chloride ions. Since the table salt solution did not contain metallic sodium or gaseous chlorine, he concluded that the sodium and chlorine particles must carry electric charges. His teachers and most of the chemists of the time found this theory too wild to believe. Electrically charged atoms were inconceivable to those who accepted Dalton’s model of the atom. Nevertheless, in 1884 Arrhenius prepared his ionic theory. It defined an acid as a compound that dissolves in water to yield hydrogen ions, and a base as a compound that dissolves in water to yield hydroxide ions. He underwent an oral exam on the theory, but was awarded only a bare passing mark by his examiners who thought the theory too farfetched. In the 1890’s, however, upheavals in science began to occur. J.J. Thomson discovered the electron and Becquerel discovered radioactivity. It soon became clear that the atom was made up of charged particles such as the negatively charged electron. Suddenly Arrhenius’ ionic theory made sense. In 1903 he won the Nobel prize in chemistry for the same theory that had earned him only a passing grade just nineteen years earlier.

9. Le pH Le pH est un mesure de la concentration d’ions d’hydrogène, [H + (aq) ]. Parenthèse carré indique concentration Aqueux: ions entourés des molécules d’eau Ion d’hydrogène

10. Acide; [H + (aq) ] > [OH - (aq) ] ;base Si [H + (aq) ] = [OH - (aq) ] alors c ’est une solution _____________ Ex. H 2 O (l) ↔ H + (aq) + OH - (aq) (HOH) renversible L’échelle du pH p219 ‘Omni 10’ [H + (aq) ] [H + (aq) = OH - (aq) ] [OH - (aq) ] 0---------------------------------7-----------------------------------14 Acide neutre alcalin/basique HCl (aq) H 2 O NaOH (aq) H 2 SO 4(aq) BTB: Phth: Litmus: neutre jaune vert bleu incolore rose Rose bleu

11. L’échelle du pH

16. Dr. Joe Schwarcz Dr. Joe p213, p68 et p158 Devoir: p218 ‘Omni 10’ #1-2