Chemistry worksheet
    Topic: Oxidation Reduction
    Oxidation Reduction
    1

    When a voltaic cell operates, ions move through the

    (1) anode

    (2) cathode

    (3) salt bridge

    (4) external circuit

    2

    Based on Reference Table J, which two reactants react spontaneously?

    (1) Mg(s) + ZnCl2(aq)

    (2) Cu(s) + FeSO4(aq)

    (3) Pb(s) + ZnCl2(aq)

    (4) Co(s) + NaCl(aq)

    3

    In an oxidation-reduction reaction, the total number of electrons lost is

    (1) equal to the total number of electrons gained

    (2) equal to the total number of protons gained

    (3) less than the total number of electrons gained

    (4) less than the total number of protons gained

    4

    Which metal will spontaneously react with Zn2+(aq), but will not spontaneously react with Mg2+(aq)?

    (1) Mn(s)

    (2) Cu(s)

    (3) Ni(s)

    (4) Ba(s)

    5

    Given the incomplete equation representing a reaction:

    moles-and-stoichiometry, formulas, oxidation-reduction, oxidation-reduction-(redox)-reaction, moles-and-stoichiometry, compounds fig: chem12013-exam_g12.png

    What is the formula of the missing product?

    (1) O2−

    (2) O2

    (3) OH

    (4) OH

    6

    In an oxidation-reduction reaction, the number of electrons lost is

    (1) equal to the number of electrons gained

    (2) equal to the number of protons gained

    (3) less than the number of electrons gained

    (4) less than the number of protons gained

    7

    Which element reacts spontaneously with 1.0 M HCl(aq) at room temperature?

    (1) copper

    (2) gold

    (3) silver

    (4) zinc

    8

    Given the balanced ionic equation:

    3Pb2+(aq) + 2Cr(s) → 3Pb(s) + 2Cr3+(aq)

    What is the number of moles of electrons gained by 3.0 moles of lead ions?

    (1) 5.0 mol

    (2) 2.0 mol

    (3) 3.0 mol

    (4) 6.0 mol

    9

    Given the balanced equation representing a reaction:

    2Al(s) + 3Cu2+(aq) → 2Al3+(aq) + 3Cu(s)

    Which particles are transferred in this reaction?

    (1) electrons

    (2) neutrons

    (3) positrons

    (4) protons

    10

    Which balanced equation represents a redox reaction?

    (1) Mg + Cl2 → MgCl2

    (2) CaO + H2O → Ca(OH)2

    (3) HNO3 + NaOH → NaNO3 + H2O

    (4) NaCl + AgNO3 → AgCl + NaNO3

    Base your answers to questions 11 on the information below.

    The diagram below represents an operating electrolytic cell used to plate silver onto a nickel key. As the cell operates, oxidation occurs at the silver electrode and the mass of the silver electrode decreases.

    oxidation-reduction, electrochemical-cell, voltaic-cell fig: chem12012-exam_g16.png

    11

    Explain, in terms of Ag atoms and Ag+(aq) ions, why the mass of the silver electrode decreases as the cell operates.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • Silver atoms lose electrons and become silver ions in the solution.

    • Some of the Ag atoms become Ag+ ions.

    • Silver atoms are oxidized to silver ions.

    Base your answers to questions 12 on the information below.

    Metallic elements are obtained from their ores by reduction. Some metals, such as zinc, lead, iron, and copper, can be obtained by heating their oxides with carbon.

    More active metals, such as aluminum, magnesium, and sodium, can not be reduced by carbon. These metals can be obtained by the electrolysis of their molten (melted) ores. The diagram below represents an incomplete cell for the electrolysis of molten NaCl. The equation below represents the reaction that occurs when the completed cell operates.

    oxidation-reduction, electrochemical-cell, electrolytic-cell fig: chem12013-exam_g20.png

    12

    Identify one metal from the passage that is more active than carbon and one metal from the passage that is less active than carbon.

    Allow 1 credit for identifying one metal from the passage that is more active than carbon and

    • one metal from the passage that is less active than carbon.

    • More active than carbon:

    • aluminum

    • Mg

    • Na

    • Less active than carbon:

    • zinc

    • Pb

    • Fe

    • copper

    Base your answers to questions 13 on the information below and on your knowledge of chemistry.

    Fossil fuels produce air pollution and may eventually be depleted. Scientists are researching ways to use hydrogen as an alternate fuel.

    A device called an artificial leaf was invented to produce hydrogen and oxygen using sunlight and water. The artifical leaf is an electrochemical cell. Equations 1 and 2 below represent the reactions taking place in the leaf. Equation 3 represents a reaction of hydrogen when used as fuel.

    Equation 1: 2H2O + energy from sunlight → O2 + 4H+ + 4e

    Equation 2: 4H+ + 4e → 2H2

    Equation 3: 2H2(g) + O2(g) → 2H2O(g) + energy

    13

    State one benefit of using the artificial leaf to produce hydrogen.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • The hydrogen could replace the use of fossil fuel.

    • The use of hydrogen as a car fuel could reduce air pollution.

    • The H2 fuel is renewable.

    • Water is a nonpolluting product.

    • The leaf uses renewable resources.

    Base your answers to questions 14 on the information below and on your knowledge of chemistry.

    The diagram and balanced ionic equation below represent two half-cells connected to produce an operating voltaic cell in a laboratory investigation. The half-cells are connected by a salt bridge.

    oxidation-reduction, oxidation-numbers-(states) fig: chem12017-exam_g19.png

    14

    State the purpose of the salt bridge in this voltaic cell.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • The salt bridge allows ions to flow between the two half-cells.

    • It maintains the electrical neutrality of the solutions.

    • prevents polarization of the half-cells

    Base your answers to questions 15 on the information below and on your knowledge of chemistry.

    A student sets up a voltaic cell using magnesium and zinc electrodes. The porous barrier in the cell has the same purpose as a salt bridge. The diagram and the ionic equation below represent this operating cell.

    moles-and-stoichiometry, chemical-reactions-and-equations fig: chem12018-exam_g17.png

    15

    State, in terms of ions, how the porous barrier functions as a salt bridge in this cell.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • The porous barrier allows for the migration of ions between the half-cells.

    • The barrier maintains electrical neutrality by allowing ions to flow.