Download problem set 3 2016

Problem Set
Aqueous Reactions and Electrochemistry
Due: November 21, 2016
1. The vanadium in a sample of ore is converted to VO2+. The VO2+ ion is
subsequently titrated with MnO4- in
2. acidic solution to form V(OH)4+ and manganese (II) ion. The unbalanced
titration reaction is:
MnO4 (aq) + VO2+(aq) + H2O(l)  V(OH)4+(aq) + Mn2+(aq) + H+(aq)
To titrate the solution, 26.45 ml of 0.02250 M MnO4- was required. If the mass
percent of vanadium in the ore was 58.1 %, what was the mass of the ore sample?
2. Balance the following equations using the half-reaction method
a. Fe(s) + HCl(aq)  HFeCl4(aq) + H2(g)
b. IO3-(aq) + I-(aq)  I33. Gold metal will not dissolve in either concentrated nitric acid or concentrated
hydrochloric acid. It will dissolve, however, in aqua regia, a mixture of the two
concentrated acids. The products of the reaction are the AuCl4- ion and gaseous NO.
Write a balanced equation for the dissolution of gold in aqua regia.
4. A zinc-copper battery is constructed as follows at 25 oC:
Zn lZn2+ ll Cu2+ l Cu
The mass of each electrode is 200 g.
a. Calculate the cell potential when this battery is first connected.
b. Calculate the mass of each electrode after 10.0 hr.
c. How long can this battery deliver a current of 10.0 A before it goes dead?
d. Draw the two electrodes and their solutions showing what is occurring
on each electrode and in the solution surrounding them. (Zn, Zn2+,Cu2+ ,
Cu)
5. Consider a galvanic cell involving iron (III) nitrate and silver and silver nitrate:
a. Draw the galvanic cell, labeling the anode, the cathode
and the direction of the electron flow.
b. Give the line notation diagram for this process.
6. An aqueous solution of an unknown salt of ruthenium is electrolyzed by a current
of 2.50 A passing for 50.0 minutes. If 2.618 g Ru is produced at the cathode, what is
the charge on the ruthenium ions in solution?
7. An unknown metal M is electrolyzed. It took 74.1 s for a current of 2.00 A to plate
out 0.107 g of the metal from a solution containing M(NO3)3. Identify the metal.
8. Three electrochemical cells were connected in series so that the same quantity of
electrical current passes through all three cells. In the first cell, 1.15 g chromium
metal was deposited from a chromium(III) nitrate solution. In the second cell, 3.15
g osmium was deposited from a solution made of Osn+1 and nitrate ions. What is the
name of the salt? In the third cell the electrical charge passed through a solution
containing X2+ ions caused deposition of 2.11 g metallic X. What is the electron
configuration of X?
9. Gold is produced electrochemically from an aqueous solution of Au(CN)2containing excess of CN-. Gold metal and oxygen gas are produced at the electrodes.
What amount of (moles) of O2 will be produced during the production of 1.00 mole
of gold?
10. Write the balanced net-ionic equations for the following reactions. Include
states
a. silver nitrate reacts with iron metal
b. iron (III) nitrate is combined with solid iron metal
d. Calcium chloride reacts with sodium metal
c. fluorine gas is bubbled into a solution of potassium iodide
d. solid iron(III) carbonate is treated with nitric acid
e. barium metal is treated with hydrochloric acid