Standard Electrode Potentials and Predicting Redox Reactions · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Electrode potentials predict the winner

Science · Chemistry · ages 17-18
Name ______________________   Date ____________

  1. Which set lists the standard conditions?

    • 273 K, 100 kPa, 1.00 mol/dm3
    • 298 K, 200 kPa, 2.00 mol/dm3
    • 298 K, 100 kPa, 1.00 mol/dm3

  2. What is the standard hydrogen electrode there for?

    • It gives all potentials a 0.00 V baseline
    • It supplies electrons to every cell
    • It keeps the temperature at 298 K

  3. A negative cell potential means the reaction as written will not go.

    Circle one:   True   False

  4. In the zinc and copper cell, which metal dissolves and why?

    • Copper, since it is the positive end
    • Zinc, since it gives up electrons at the negative end
    • Neither, since both metals plate out

  5. Zinc is -0.76 V and copper is +0.34 V. Work out the standard cell potential in volts.

    Answer: ______________

  6. Why are the conditions fixed when measuring standard potentials?

    • So the voltmeter gives whole numbers
    • So values compare fairly with each other
    • So every reaction becomes feasible

  7. If Ecell is positive, the more positive half cell is the one that gets reduced.

    Circle one:   True   False

  8. A proposed reaction has Ecell = +0.50 V but nothing happens in the beaker. What is the best explanation?

    • The positive sign proves the data must be wrong
    • A huge activation barrier is freezing a feasible reaction
    • The reaction is going backwards instead
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Electrode potentials predict the winner W1-mt_LDI10CjoAI-s1

  1. 298 K, 100 kPa, 1.00 mol/dm3 · Standard is 298 K, 100 kPa and 1.00 mol/dm3, fixed so values compare fairly.
  2. It gives all potentials a 0.00 V baseline · Single electrodes cannot be measured alone, so hydrogen is defined as zero for comparison.
  3. True · Only a positive value means feasible as written. The sentence is true.
  4. Zinc, since it gives up electrons at the negative end · Zinc is oxidised at the negative end, so its atoms enter the solution as ions.
  5. 1.1 · Ecell = 0.34 minus -0.76 = +1.10 V.
  6. So values compare fairly with each other · Potentials shift with conditions, so fixed values keep the ranking fair.
  7. True · The positive end gains the electrons. In Zn/Cu that is copper plating out. The sentence is true.
  8. A huge activation barrier is freezing a feasible reaction · Feasible is not the same as fast. Kinetics can stall a reaction with a positive Ecell.
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