tailieunhanh - Chemistry part 32, Julia Burdge,2e (2009)

Tham khảo sách 'chemistry part 32, julia burdge,2e (2009)', khoa học tự nhiên, hoá học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 786 CHAPTER 19 Electrochemistry Applying What The pain caused by having aluminum foil contact a dental filling results from the filling being made the cathode in an electrochemical cell. Another type of discomfort can result from the filling being made the anode in an electrochemical cell. This occurs when the filling touches a metal with a greater reduction potential than the components of the amalgam such as gold. When an amalgam filling comes into contact with a gold inlay the tin in the filling the most easily oxidized of the major amalgam components is oxidized creating an unpleasant metallic taste in the mouth. A simplified unbalanced equation for the redox reaction that takes place is Sn s O2 g ------ Sn2 a H O Dental filling Gold inlay touching amalgam dental filling Problems a Balance in acidic medium the equation for the oxidation of tin from an amalgam filling. M4 Sample Problem b Calculate the standard cell potential for the reaction in part a . H4 Sample Problem c Which of the components of dental amalgam mercury silver tin copper or zinc would be oxidized when a filling is brought into contact with lead J44 Sample Problem d Calculate the standard free-energy change for the reaction in part a . M4 Sample Problem e Calculate the equilibrium constant at 25 C for the reaction in part a . K4 Sample Problem KEY WORDS 787 Chapter Summary Section Redox reactions are those in which oxidation numbers change. Halfreactions are the separated oxidation and reduction reactions that make up the overall redox reaction. Redox equations can be balanced via the half-reaction method which allows for the addition of H2O to balance O H to balance H and OH- for reactions taking place in basic solution. Section An electrochemical cell in which a spontaneous chemical reaction generates a flow of electrons through a wire is called a galvanic cell. Half-reactions in a galvanic cell take place in separate compartments called half-cells. .