AP Chemistry - Electrochemistry Worksheet #3
Half-Cell Balancing
1. Balance these equations for reactions occurring in acidic solution.

(a) Sn  +  NO3- ----> SnO2 + NO 

(b) Ag + NO3- ---> NO2 + Ag+

(c) Fe3+ + NH4OH+ ----> Fe2+ + N2

(d) HNO2 + I- ---> I2 + NO 

(e) C2O42- + HNO2 ---> CO2 + NO 

(f) HNO2 + MnO4- ---> Mn2+ + NO3-

(g) H3PO2 + Cr2O72- ---> H3PO4 + Cr3+

(h) VO2+ + Sn2+ ---> VO2+ + Sn4+

(i) XeF2 + Cl- ---> Xe + F- + Cl2
 
2. Balance the following equations by the ion-electron method. 

a) NBr3 ---> N2 + Br- + HOBr (basic solution) 

(b) ClNO2 -----> NO3- + Cl- (acidic solution) 

(c) Cl2 ---> Cl- + ClO3- (basic solution) 

(d) H2SeO3 + H2S -----> S + Se (acidic solution) 

(e) MnO2 + SO32- ---> Mn2+ + S2O62- (acidic solution) 

(f) BrO3F -----> BrO4- + F- (basic solution) 

(g) XeO3 + I- ----> Xe + I2 (acidic solution) 

(h) HXeO4- ----> XeO64- + Xe + O2 (basic solution) 

(i) (CN)2 -----> CN- + OCN- (basic solution) 
 
3. Complete and balance the following reaction which occur in basic solution.

a) Al + NO3- + OH- ---> Al(OH)4- + NH3

b) PbO2 + Cl- ---> ClO- + Pb(OH)3-

c) N2H4 + Cu(OH)2 ---> N2 + Cu 

d)  Ag2S + CN- + O2 ---> S + Ag(CN)2-

e)  ClO- + Fe(OH)3 ---> Cl- + FeO42-

f)  HO2- + Cr(OH)3- ---> CrO42- + OH-

g)  ClO2 + OH- ---> ClO2- + ClO3-

h)  V + H2O ---> VH6O173- + H2

i)  Mn(CN)64- + O2 ---> Mn(CN)63-
 
4.  Lead(IV) oxide reacts with hydrochloric acid to give chlorine. The equation for the reaction is 

PbO2 + 4 Cl- + 4H+ ------> PbCl2 + 2 H2O + Cl2

How many gram of chlorine are formed from 150 g of PbO2
 
5. Manganese(II) ion is oxidized to permanganate ion by bismuthate ion, BiO3-, in an acidic solution. In the reaction, BiO3- is reduced to Bi+

(a) Write a balanced net ionic equation for the reaction. 

(b) How many grams of NaBiO3 are needed to oxidize the manganese in 15.0 g of Mn(NO3)2
 
6. A sample of a chromium-containing alloy weighing 3.000 g was dissolved in acid, and all the chromium in the sample was oxidized to CrO42-. It was then found that 3.09 g of Na2SO3 was required to reduce the CrO42- to Cr(OH)3 in a basic solution, with the SO32- being oxidized to SO42-.

(a) Write a balanced equation for the reaction of CrO42- with SO32-

(b) How many moles of CrO42- reacted with Na2SO3?

(c) How many grams of Cr were in the alloy sample? 

(d) What is the weight percentage of Cr in the alloy? 
 
7. A sample of a tin ore weighing 0.3000 g was dissolved in an acid solution and all the tin in the sample was changed to tin(II). The solution was titrated with 8.08 mL of 0.0500 M KMnO4 solution, which was oxidized the tin(II) to tin(IV). 

(a) What is the balanced equation for the reaction in the titration?

(b) How many grams of tin were in the sample? 

(c) What was the percentage by weight of tin in the sample? 

(d) If the tin in the sample had been present in the compound SnO2, what would have been the percentage by weight of SnO2 in the sample?