Cell Notation

Clues to cocaine's toxicity could lead to better tests for its detection in biofluids

               

A new study on cocaine, the notorious white powder illegally snorted, injected or smoked by nearly 2 million Americans, details how it may permanently damage proteins in the body. That information, gleaned from laboratory tests, could be used to potentially detect the drug in biofluids for weeks or months—instead of days—after use, say scientists. The findings, which appear in the ACS journal Chemical Research in Toxicology, could also help explain cocaine's long-term health effect

cell at equilibrium

• When the cell reaction is at equilibrium, the reaction quotient Q is equal to the equilibrium constant; Q=K
• cell at equilibrium can not do work
• Potential difference, E=0

        The equilibrium constant, K, for the cell is derived using a derivative of the                                  Nernst equation:

                                                       ln K = nFE0/RT

      where F is the Faraday constant,

                  R is the gas constant, 

                  T is the temperature in kelvins.

Concentration Cell

A concentration cell is an electrolytic cell that is comprised of two half-cells with the same electrodes, but differing in concentrations. A concentration cell acts to dilute the more concentrated solution and concentrate the more dilute solution, creating a voltage as the cell reaches an equilibrium. This is achieved by transferring the electrons from the cell with the lower concentration to the cell with the higher concentration.

Problems

 Calculate cell potential for a concentration cell with two silver electrodes with concentrations 0.2M and 3.0M.

SOLUTION:

Reaction:

Ag2++2e−→Ag(s)

Cell Diagram:

Ag(s)|Ag2+(0.2M)||Ag2+(3.0M)|Ag(s)

Nernst Equation:

E=Eo−0.05922log 0.23.0

  **Eo = 0 for concentration cells

                       E = 0.0644V

Nernst Equation

Related the zero current potential to the activities of the participants in the cell reaction

                   (half-cell reduction potential)

           

                  (total cell potential) (Q)- Reaction Quotient

liquid junction potential

• In a cell when two different electrolytes are in contact, an additional source of potential difference occur across the interface of the two electrolytes  
• That is called liquid junction potential

Isomerism in Coordination Compounds

                                Isomerism in Coordination Compounds

Isomers are two or more compounds that have the same chemical formula but a different arrangement of atoms. Because of the different arrangement of atoms, they differ in one or more physical or chemical properties. Two principal types of isomerism are known among coordination compounds. Each of which can be further subdivided. 

(a) Stereoisomerism

               (i) Geometrical isomerism           (ii) Optical isomerism

 (b) Structural isomerism

                 (i) Linkage isomerism                 (ii) Coordination isomerism                                                                 (iii) Ionisation isomerism             (iv) Solvate isomerism 

Stereoisomers have the same chemical formula and chemical bonds but they have different spatial arrangement. Structural isomers have different bonds. A detailed account of these isomers are given below.

•   Geometric Isomerism

                The facial (fac) and meridional (mer) isomers of [Co(NH3 )3(NO2 )3]