Thermochemistry

Chapter 20



Zn(s) + H+(aq) ---> Zn+2(aq) + H2(aq)


Section 20-1


Zn(s) + H+(aq) ---> Zn+2(aq) + H2(aq)



Cd(s) + NiO2(s) + 2H2O(l) ---> Cd(OH)2(s) + Ni(OH)2(s)




Section 20-2

Balancing Redox Reactions


Sn+2(aq) + 2Fe+3(aq) ---> Sn+4(aq) + 2Fe+2(aq)



Oxidation: Sn+2(aq) ---> Sn+4(aq) + 2 e-

Reduction: 2Fe+3(aq) + 2e- ---> 2Fe+2(aq)


Cu(s) + NO3(aq)- ---> Cu+2(aq) + NO2(aq)

Cu(s) ---> Cu+2(aq)

NO3-(aq) ---> NO2(g)


(add water to balance oxygens)

NO3-(aq) ---> NO2(g) + H2O(l)

(add hydrogen ions to balance hydrogens)

2H+ + NO3-(aq) ---> NO2(g) + H2O(l)

(add electrons to balance charges)

1e- + 2H+ + NO3-(aq) ---> NO2(g) + H2O(l)

Cu(s) ---> Cu+2(aq) + 2e-

(multiply through by an integer to get the electrons gained to equal the electrons lost)

Cu(s) ---> Cu+2(aq) + 2e-

2e- + 4H+ + 2NO3-(aq) ---> 2NO2(g) + 2H2O(l)

(add the two equations together--cancelling out on both sides of the equation)

Cu(s) + 4H+ + 2NO3-(aq) ---> Cu+2(aq) + 2NO2(g) + 2H2O(l)



Basic Solutions

Section 20-3

Voltaic Cells - used to perform electrical work