Chapter U5.19, Problem 5E

Interpretation Introduction

Interpretation:

The combination of metal that will result in the greatest voltage must be predicted with explanation. Also, voltage must be calculated for the redox reaction to check whether prediction was correct or not.

Concept Introduction:

Voltage of an electrochemical cell is the difference of electrode potential between cathode and anode.

Answer to Problem 5E

Electrochemical cell with iron and calcium will have greatest voltage.

Cell voltage ${\text{=E}}^{\text{0}}{}_{\text{cathode}}{\text{-E}}^{\text{0}}{}_{\text{anode}}\text{=0}\text{.77V-(-2}\text{.76)V=(0}\text{.77+2}\text{.76)V=3}\text{.53V}\text{.}$

Explanation of Solution

Higher the position of a metal in the electrochemical series stronger is the reducing power and higher negative is the reduction potential.

Lower the position of a metal in the electrochemical series stronger is the oxidizing power and higher positive is the reduction potential.

Accordingly, combination of Calcium and iron is considered.

For iron and calcium cell

Cell voltage ${\text{=E}}^{\text{0}}{}_{\text{cathode}}{\text{-E}}^{\text{0}}{}_{\text{anode}}\text{=0}\text{.77V-(-2}\text{.76)V=(0}\text{.77+2}\text{.76)V=3}\text{.53V}\text{.}$

For copper and tin cell

Cell voltage ${\text{=E}}^{\text{0}}{}_{\text{cathode}}{\text{-E}}^{\text{0}}{}_{\text{anode}}\text{=0}\text{.34V-(-0}\text{.14)V=(0}\text{.34+0}\text{.14)V=0}\text{.48V}\text{.}$

For silver and aluminium cell

Cell voltage ${\text{=E}}^{\text{0}}{}_{\text{cathode}}{\text{-E}}^{\text{0}}{}_{\text{anode}}\text{=0}\text{.80V-(-1}\text{.66)V=(0}\text{.80+1}\text{.66)V=2}\text{.46V}\text{.}$

For copper and lead cell

Cell voltage ${\text{=E}}^{\text{0}}{}_{\text{cathode}}{\text{-E}}^{\text{0}}{}_{\text{anode}}\text{=0}\text{.34V-(-0}\text{.13)V=(0}\text{.34+0}\text{.13)V=0}\text{.47V}\text{.}$

The calculations show that the voltage of the cell is greatest among all the given cells and thus the prediction was correct.

Conclusion

Greatest voltage cell was predicted from the given combination of metals. Prediction which matched with voltage calculation was correct.