Redox answers - Tully School District

Name:_______________________________
Given the balanced equation representing a reaction:
1) ____ During this reaction, the oxidation number of Fe changes from
a) +2 to 0 as electrons are transferred
b) +2 to 0 as protons are transferred
c) +3 to 0 as electrons are transferred
d) +3 to 0 as protons are transferred
Base your answers to questions 2 through 4 on the information below.
A voltaic cell with magnesium and copper electrodes is shown in the
diagram below. The copper electrode has a mass of 15.0 grams. When the
switch is closed, the reaction in the cell begins. The balanced ionic equation
for the reaction in the cell is shown below the cell diagram. After several
hours, the copper electrode is removed, rinsed with water, and dried. At this
time, the mass of the copper electrode is greater than 15.0 grams.
2) State the direction of electron flow through the wire between the
electrodes when the switch is closed.
3) State the purpose of the salt bridge in this cell.
4) Explain, in terms of copper ions and copper atoms, why the mass of the copper electrode increases as the cell
operates. Your response must include information about both copper ions and copper atoms.
Base your answers to questions 6 through 8 on the information below.
In a laboratory investigation, a student constructs a voltaic cell with iron and copper electrodes. Another student
constructs a voltaic cell with zinc and iron electrodes. Testing the cells during operation enables the students to write the
balanced ionic equations below.
5) State evidence from the balanced equation for the cell with iron and copper electrodes that indicates the reaction in
the cell is an oxidation-reduction reaction.
6) Identify the particles transferred between Fe 2+ and Zn during the reaction in the cell with zinc and iron electrodes. ____________
7) Write a balanced half-reaction equation for the reduction that takes place in the cell with zinc and iron electrodes.
8) State the relative activity of the three metals used in these two voltaic cells.
Regent Review – Redox Reaction 1-2 Created: February 2010

Name:_______________________________
9) ____ Which substance can be broken down by chemical means?
a) magnesium
b) manganese
c) mercury
d) methanol
10) ____ The diagram below represents an operating electrochemical cell
and the balanced ionic equation for the reaction occurring in the cell.
Which statement identifies the part of the cell that conducts electrons
and describes the direction of electron flow as the cell operates?
a) Electrons flow through the salt bridge from the Ni(s) to the Zn(s).
b) Electrons flow through the salt bridge from the Zn(s) to the Ni(s).
c) Electrons flow through the wire from the Ni(s) to the Zn(s).
d) Electrons flow through the wire from the Zn(s) to the Ni(s).
Base your answers to questions 11 through 13 on the information below.
In a laboratory investigation, magnesium reacts with hydrochloric acid to produce hydrogen gas and magnesium chloride.
This reaction is represented by the unbalanced equation below.
11) State, in terms of the relative activity of elements, why this reaction is spontaneous.
12) Balance the equation, using the smallest whole-number coefficients.
13) Write a balanced half-reaction equation for the oxidation that occurs.
Base your answers to questions 14 through 16 on the
information below.
The diagram below shows a system in which water is
being decomposed into oxygen gas and hydrogen gas.
Litmus is used as an indicator in the water. The litmus
turns red in test tube 1 and blue in test tube 2.
The oxidation and reduction occurring in the test tubes
are represented by the balanced equations below.
14) Identify the information in the diagram that indicates this system is an electrolytic cell.
15 ) Determine the change in oxidation number of oxygen during the reaction in test tube 1. ______________________
16)
Explain, in terms of the products formed in test tube 2, why litmus turns blue in test tube 2.
Regent Review – Redox Reaction 2-2 Created: February 2010