|AP Chemistry - Electrochemistry Worksheet #8|
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?
reacts with sodium sulphite according to the equation
NaIO3 + 3 Na2SO3 -----> 3 Na2SO4 + NaI
(a) In this reaction, which substance is the oxidizing agent?
|3.||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?
|4.||Solder is an
alloy containing the metals tin and lead. A particular sample of this alloy
weighing 1.50 g was dissolved in acid. All the tin was then converted
to the +2 oxidation state. Next, it was found that 0.368 g of Na2Cr2O7
was required to oxidize the Sn2+ to Sn4+ in an acidic
solution. In the reaction the chromium was reduced to Cr3+ ion.
(a) Write a balanced net ionic equation for the reaction between the Sn2+ and Cr2O72- in an acidic solution.
(b) Calculate the number of grams of tin that were in the sample of solder.
(c) What was the percentage by weight of tin in the solder?
|5.||All the iron
in a 2.000 g sample of an iron ore was dissolved in an acidic solution and
converted to Fe2+, which was then titrated with 0.1000 M KMnO4
solution. In the titration the iron was oxidized to Fe3+.
The titration required 27.45 mL of the KMnO4 solution.
(a) How many grams of iron were in the sample?
(b) What was the percentage iron in the sample?
(c) If the iron was present in the sample as Fe2O3, what was the percentage by weight of Fe2O3 in the sample?
|6.||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)
(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?
|7.||A sample weighing
0.2000 g was known to contain CuSO4. It was dissolved
in water and the copper in the solution was allowed to react with a solution
containing excess iodide ion. The I3- that was formed was titrated
with 0.01000 M Na2S2O3 solution using
starch as an indicator. The titration required 35.65 mL of the thiosulphate
solution. What was the percentage by weight of CuSO4 in
the original 0.2000 g sample?
|8.||A 1.00 mL sample
of household bleach, which contains sodium hypochlorite, NaOCl, was added
to a solution containing excess iodide ion. The hypochlorite reacts
with iodide ion as follows.
2 H+ + OCl- + 3 I- -----> I31- + Cl- + H2O
After the reaction, the I31-
was titrated with a 0.0500 M solution of Na2S2O3,
using starch as an indicator. The titration required 28.20 mL of the
|9.||How many millilitres
of Cl2 gas, measured at 25oC and
98.66 kPa, are needed to react with 10.0 mL of 0.10 M NaI
if the I1- is oxidized to IO31-and Cl2 is reduced to Cl1-?
the solubility of copper(II) iodate, Cu(IO3)2, by
iodometric titration in an acidic solution at 25oC we start
with 20.00 cm3 of a saturated aqueous solution and 30.00 cm3
of a 0.100 molar sodium thiosulphate solution are needed.
a) Write the sequence of a balanced equation for the chemical reaction.
b) Calculate the initial concentration of Cu2+ ions in the solution.
c) Determine the solubility product, Ksp, of copper(II) iodate (including the units). Ignore activity coefficients.
plant produces 50,000 tonnes of aluminum per year. If the plant
is in operation at all times (even holidays), what current must flow to
give this production?
cells are in series. In one there is a solution of copper(II) sulphate
,CuSO4, and in the other there is a solution of copper(II) chloride
in hydrochloric acid ( the complex ion CuCl2- is the predominant
species). How much copper metal will be deposited at the cathode in
each cell if a current of 6.00 amperes flows for 2.00 hours?
|13.||A sample of pure
Fe3O4 weighing 0.4532 g is dissolved in dilute sulphuric
acid and then titrated with 0.02430 M KMnO4. What volume
of permanganate solution is required?
|14.||If 4 g of Li
reacts with excess H2,
a) how many moles of electrons are transferred from Li to H?
b) how many electrons?
|15.||Excess KI solution
was added to 10 mL of a solution containing Cu2+. After reaction
had ceased, 5.5 mL of 0.1 M Na2S2O3 solution
was required to completely change the brown colour of the solution to colourless.
How much Cu2+ did the original solution contain?
weight of copper deposited by the flow of 24,125 coulombs of electricity
through a solution of copper(II) sulphate.
number of coulombs of electricity that pass through a circuit when 5 amperes
flow for 2 hours.
number of coulombs required to liberate
a) 22.4 L of H2 at STP.
b) 44.8 L of O2 at STP
c) 27.42 g of Fe from an Fe3+ ion solution.
|19.||A current of
0.4 amps flow for 2.5 hours through a solution of
Calculate the weight or volumes at STP of the products formed at the electrodes.
|20.||An electric current,
passing through a solution of CuSO4, liberates 15.9 g of metallic
copper. How many grams of silver will be liberated by the same amount
|21||When a solution
of ZnSO4 is electrolyzed, the following reaction takes place:
2 ZnSO4 + 2 H2O ----> 2 Zn + 2 H2SO4 + O2
If 13 g of zinc are plated out, what weight of oxygen gas is
liberated simultaneously? what volume of oxygen, measured at STP is
of electricity are passed through a dilute solution of H2SO4.
Calculate the weights of the materials produced at the anode and cathode
|23.||How many coulombs
of electricity are required to:
a) develop 0.4 amp flow for 2 hours?
b) liberate 11.2 L of H2 at STP?
c) liberate 11.2 L of O2 at STP,
d) liberate 22.4 L of Cl2 at STP,
e) deposit 0.1 g of Ag,
f) deposit 1 g of Fe from (1) Fe2+ solution and (2) Fe3+ solution.
|24.||A solution of
copper(II) sulphate is electrolyzed between inert electrodes.
a) How many minutes must a current of 2.6 amp flow to deposit 6 g of Cu metal?
b) What strength of current must flow for 1.5 hours to deposit 4.8 g of Cu metal?
|25.||In an electric
current, flowing for a certain time, plates out 54 g of silver from a solution
of AgNO3, how many grams of lead will the same current deposit
during an equal time period from a solution of lead nitrate, Pb(NO3)2.
of electricity are passed successively through solutions of
a) aluminum chloride,
b) dilute sulphuric acid,
c) hydrochloric acid,
d) copper(II) sulphate.
If 11.2 L of chlorine at STP are liberated from the solution:
|27.||A current of
0.04 amp passed through a solution of silver nitrate deposits 0.16 g of
silver. Calculate the volume of H2 at STP that would be
liberated from a aqueous KCl solution by the same quantity of current.
|28.||What mass of
MnO2 is reduced by 45.5 cm3 of 0.30 N oxalic acid,
H2C2O4, in sulphuric acid solution?
The unbalanced equation is
MnO2 + H+ + H2C2O4 ----> CO2 + H2O + Mn2+