An Introductory Course of Quantitative Chemical Analysis eBook


!Answer!:  0.992 gram; 1.97 cc.

103.  One gram of a mixture of silver chloride and silver bromide is found to contain 0.6635 gram of silver.  What is the percentage of bromine?

!Answer!:  21.30%.

104.  A precipitate of silver chloride and silver bromide weighs 0.8132 gram.  On heating in a current of chlorine, the silver bromide is converted to silver chloride, and the mixture loses 0.1450 gram in weight.  Calculate the percentage of chlorine in the original precipitate.

!Answer!:  6.13%.

105.  A sample of feldspar weighing 1.000 gram is fused and the silica determined.  The weight of silica is 0.6460 gram.  This is fused with 4 grams of sodium carbonate.  How many grams of the carbonate actually combined with the silica in fusion, and what was the loss in weight due to carbon dioxide during the fusion?

!Answers!:  1.135 grams; 0.4715 gram.

106.  A mixture of barium oxide and calcium oxide weighing 2.2120 grams is transformed into mixed sulphates, weighing 5.023 grams.  Calculate the grams of calcium oxide and barium oxide in the mixture.

!Answers!:  1.824 grams CaO; 0.3877 gram BaO.



The following brief statements concerning the ionic theory and a few of its applications are intended for reference in connection with the explanations which are given in the Notes accompanying the various procedures.  The reader who desires a more extended discussion of the fundamental theory and its uses is referred to such books as Talbot and Blanchard’s !Electrolytic Dissociation Theory! (Macmillan Company), or Alexander Smith’s !Introduction to General Inorganic Chemistry! (Century Company).

The !electrolytic dissociation theory!, as propounded by Arrhenius in 1887, assumes that acids, bases, and salts (that is, electrolytes) in aqueous solution are dissociated to a greater or less extent into !ions!.  These ions are assumed to be electrically charged atoms or groups of atoms, as, for example, H^{+} and Br^{-} from hydrobromic acid, Na^{+} and Oh^{-} from sodium hydroxide, 2NH_{4}^{+} and so_{4}^{—­} from ammonium sulphate.  The unit charge is that which is dissociated with a hydrogen ion.  Those upon other ions vary in sign and number according to the chemical character and valence of the atoms or radicals of which the ions are composed.  In any solution the aggregate of the positive charges upon the positive ions (!cations!) must always balance the aggregate negative charges upon the negative ions (!anions!).

It is assumed that the Na^{+} ion, for example, differs from the sodium atom in behavior because of the very considerable electrical charge which it carries and which, as just stated, must, in an electrically neutral solution, be balanced by a corresponding negative charge on some other ion.  When an electric current is passed through a solution of an electrolyte the ions move with and convey the current, and when the cations come into contact with the negatively charged cathode they lose their charges, and the resulting electrically neutral atoms (or radicals) are liberated as such, or else enter at once into chemical reaction with the components of the solution.

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