CONSTRUCTING RELATIVE REACTIVITY TABLES

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CONSTRUCTING RELATIVEREACTIVITY TABLES
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• we will examine the observations made when a
  group of elements and their ions are mixed
  together.
• We will then arrange these elements into a table
  showing relative reactivity.
• This could be in terms of the easiest to the most
  difficult to be oxidized or reduced or in terms
  of the best/worst oxidizing agent or reducing
  agent

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SAMPLE PROBLEM 1

• Four elements, A, B, C, and D, form diatomic
  molecules and ions with a 1- charge.
• B- C2 ? C- B2
• A- C2 ? No Reaction
• D- B2 ? B- D2

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• Write the equation for each reduction half
  reaction.
• Arrange the equations in a relative reduction
  potential table with the easiest to reduce at the
  top and the hardest to reduce at the bottom.
• c) Write the equation for each oxidation half
  reaction.
• d) Arrange the equations in a relative oxidation
  potential table with the easiest to oxidize at
  the top and the hardest to oxidize at the bottom.
• e) Which is the best oxidizing agent? Which is
  the best reducing agent?

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SAMPLE ANSWER 1

• The reduction half reactions are
• C2 2e- ? 2C-
• B2 2e- ? 2B-
• A2 2e- ? 2A-
• D2 2e- ? 2D-

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• b) Equation (2) indicates no reaction. However,
  this means no forward reaction. The reverse
  reaction will take place
• C- A2 ? A- C2
• C2 reacts with B-, ? C2 is above B2 in table
• A2 reacts with C-, ? A2 is above C2
• B2 reacts with D-, ? B2 is above D2
• This works out to A2 is above C2 , C2 is above B2
  , and B2 is above D2 .

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Table for (b)

• Reactivity table for reduction half reactions,
  easiest to reduce top, hardest on bottom
• A2 2e- ? 2A-
• C2 2e- ? 2C-
• B2 2e- ? 2B-
• D2 2e- ? 2D-

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• c) The oxidation half reactions are
• 2A- ? A2 2e-
• 2C- ? C2 2e-
• 2B- ? B2 2e-
• 2D- ? D2 2e

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• d)
• B- reacts with C2, ? B- is above C
• C- reacts with A2, ? C- is above A
• D-reacts with B2, ? D- is above B
• So, D-is above B-, B- is above C-, and C- is
  above A-.
• 2D- ? D2 2e-
• 2B- ? B2 2e-
• 2C- ? C2 2e-
• 2A- ? A2 2e-
• e) The best oxidizing agent is the one that is
  easiest to reduce, A2. The best reducing agent is
  the one that is easiest to oxidize, D-.

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SAMPLE PROBLEM 2

• Four metals, Ca, Mn, Pb, and Mg and their ions
  with a 2 charges were involved in experiments
  that gave the following results
• 1. Mg Mn 2 ? Mg 2 Mn
• 2. Mg 2 Ca ? Mg Ca 2
• 3. Pb Mn 2 ? No Reaction

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• a) Write the equation for each reduction half
  reaction.
• b) Arrange the equations in a relative reduction
  potential table with the easiest to reduce at the
  top and the hardest to reduce at the bottom.
• c) Write the equation for each oxidation half
  reaction.
• d) Arrange the equations in a relative oxidation
  potential table with the easiest to oxidize at
  the top and the hardest to oxidize at the bottom.

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Practice 3

• Experiments were performed with 4 metals and
  solutions of their positive ions Zn/Zn2 , Fe/Fe
  2 ,Ag/Ag , Cu/Cu 2 .The following observations
  were made
• i) Fe 2 Zn ? Fe Zn 2
• ii) Fe 2 Cu ? No Reaction
• iii) 2Ag Cu ? 2Ag Cu 2
• Answer parts a to e, like previous sample
  problems.