Chapter 19, Problem 19.150MP

Interpretation Introduction

(a)

Interpretation:

A balanced equation for the reaction between hydrochloric acid and potassium permanganate should be written

Concept introduction:

When balancing half-cell reactions occur in acidic or basic medium, additional rules mustbe followed.

• First the elements in the reaction except oxygen and hydrogen should be balanced.
• Oxygen atoms are balanced by adding water molecules to opposite side of the equation.
• Hydrogen atoms are balanced by adding ${\text{H}}^{+}$ ions to the opposite side of the equation. In basic medium, ${\text{OH}}^{-}$ ions are added to neutralize ${\text{H}}^{+}$ ions in the final step.
• Charges are made equal by adding electrons to more positive side.

Interpretation Introduction

(b)

Interpretation:

The value of $E^0\text{ and }\Delta {\text{G}}^0$ for the reaction should be calculated.

Concept introduction:

The standard cell potential of overall reaction is given by the sum of the standard half-cell potentials for oxidation and reduction.

${\text{E}}_{overall}^0={\text{E}}_{ox}^0+{\text{ E}}_{red}^0$

The change in standard Gibbs free energy can be represented as follows:

$\begin{array}{l}\Delta G^0=-nF{E}^0\\ \\ \Delta G^0=\text{ Standard Gibbs free energy}\\ \text{n = number of moles of electrons transferred}\\ \text{F = Faraday constant}\\ {\text{E}}^0=\text{ Standard cell potential}\end{array}$

Interpretation Introduction

(c)

Interpretation:

Number of liters of chlorine gas at $1.0\text{ atm}$ and ${25}^0\text{ C}$ will result from the reaction of $179{\text{ g of KMnO}}_4$ with an excess of $\text{HCl}$ should be calculated.

Concept introduction:

The ideal gas equation is represented as follows:

$PV=nRT$

Here,

$\begin{array}{l}P=\text{Pressure}\\ V=\text{Volume}\\ n=\text{ Number of moles}\\ R=\text{ Universal gas constant}\\ T=\text{ Absolute temperature}\end{array}$