58. What must be the ratio of acetate ion concentration to acetic acid concentration in an aqueous solution in order to provide a solution of pH 5? The Kaof acetic acid is 1.8 x 10¯5. (A) 0.056(B) 1.0(C) 1.8(D) 5.0 59. The compound often used to provide a mild oxidizing condition in water for bleaching and for disinfecting is 60. The highest oxidation number commonly observed for anyionic or molecular transition metal species is 61. In the electrolytic refining of copper, an electric current is passed through a cell containing a pure copper electrode, an electrode of impure copper, and an aqueous solution containing copper cations. As metallic copper is removed fromthe impure electrode and redeposited on the pure copper electrode other metallic impurities are left behind if the potential of the cell is adjusted properly. In this process, the impure copper electrode is called the 62. Given the standard electrode (reduction) potentials:Ni2+(aq) + 2e¯ ---> Ni(s)E° = - 0.23 VCr3+(aq) + 3e¯ ---> Cr(s)E° = - 0.74 VWhich pair of substances will react spontaneously? (A) Ni2+with Cr3+(B) Ni with Cr3+(C) Ni2+with Cr(D) Ni with Cr 63. A certain solid-state ion-selective electrode responds according to the equationE = constant + 0.0591 log(aM2+)1/2where aM2+is the activity of a divalent cation M2+. The potential of the electrode was measured to be 0.2500 V when the electrode was immersed in a solution of Cu2+with an activity, aCu2+, of 2.0 x 10¯4M. The potential of the electrode in an unknown solution of Cu2+was 0.2796 V. The activity of the Cu2+in the unknown solution is 64. A mixed precipitate of NaCl and KCl weighing 0.2076 gram was dissolved and titrated with silver nitrate. The titration required 28.50 mL of 0.1055 M AgNO3. What was theweight percent of NaCl in the mixed precipitate? 65. The most precise meausurement of an atomic or molecularweight on the 13C mass scale is by 66. Indifferent electrolytic solutions, that is solutions containing ions other than those involved in the analysis, are used to wash precipitates rather than distilled water because (A) the wash solution must be able to conduct electrical current. (B) precipitates are too insoluble in distilled water. (C) the indifferent electrolytes prevent peptization (dispersion) of the precipitated salt. (D) the precipitated solid must be kept in the colloidal state.
You've reached the end of your free preview.
Want to read all 9 pages?