Electrochemistry Practice Flashcards

These flashcards cover the fundamental principles of electrochemistry, including galvanic and electrolytic cells, Nernst equation, conductance, molar conductivity, Faraday's laws, and commercial batteries as described in the Unit 2 lecture notes.

What is the definition of electrochemistry?

The study of production of electricity from energy released during spontaneous chemical reactions and the use of electrical energy to bring about non-spontaneous chemical transformations.

What is the overall redox reaction that occurs in a Daniell cell?

$$Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)$$

What is the electrical potential of a Daniell cell when the concentration of $Zn^{2+}$ and $Cu^{2+}$ ions is unity ($1\,mol\,dm^{-3}$)?

$$1.1\,V$$

What occurs in a Daniell cell if the external opposite potential ($E_{ext}$) exceeds $1.1\,V$?

The reaction starts to take place in the opposite direction, and the device functions as an electrolytic cell where electrons flow from $Cu$ to $Zn$.

What is a galvanic or voltaic cell?

An electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy.

According to IUPAC convention, what are standard reduction potentials now called?

Standard electrode potentials.

In a galvanic cell, what is the anode and where is it represented in a standard cell diagram?

The anode is the half-cell where oxidation takes place, and by convention, it is placed on the left side while representing the cell.

What is the formula to calculate the cell electromotive force (emf)?

$$E_{cell} = E_{right} - E_{left}$$

How is a Standard Hydrogen Electrode (SHE) represented and what is its assigned potential?

It is represented as $Pt(s)|H_{2}(g)|H^{+}(aq)$ and is assigned a potential of $0\,V$ at all temperatures.

What does a positive value of the standard electrode potential for a half-cell coupled with SHE indicate?

It indicates that the oxidized form of the species gets reduced more easily than $H^{+}$ ions.

According to Table 2.1, which species is the strongest oxidising agent and which is the most powerful reducing agent?

Fluorine gas ($F_{2}$) is the strongest oxidising agent and Lithium metal ($Li$) is the most powerful reducing agent.

What is the Nernst equation for a general electrode reaction $M^{n+}(aq) + ne^{-} \rightarrow M(s)$?

$$E_{(M^{n+}/M)} = E^{o}_{(M^{n+}/M)} - \frac{RT}{nF} \ln \frac{1}{[M^{n+}]}$$

How is the equilibrium constant ($K_{c}$) related to the standard potential of the cell ($E^{o}_{cell}$) at $298\,K$?

$$E^{o}_{cell} = \frac{0.059\,V}{n} \log K_{c}$$

What is the relationship between the standard Gibbs energy of a reaction ($\Delta_{r}G^{o}$) and the standard cell potential?

$$\Delta_{r}G^{o} = -nFE^{o}_{cell}$$

What are the SI units for resistance ($R$) and resistivity ($\rho$)?

Resistance is measured in ohm ($\Omega$) and resistivity is measured in ohm metre ($\Omega\,m$).

What is the relationship between conductance ($G$) and conductivity ($\kappa$)?

$G = \kappa \frac{A}{l}$ or $\kappa = G \times \frac{l}{A}$

What is the formula for molar conductivity ($\Lambda_{m}$)?

$\Lambda_{m} = \frac{\kappa}{c}$ where $\kappa$ is conductivity and $c$ is concentration.

What is the definition of limiting molar conductivity ($\Lambda^{o}_{m}$)?

The molar conductivity of a solution when the concentration approaches zero.

What does Kohlrausch law of independent migration of ions state?

The limiting molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation of the electrolyte.

State Faraday's First Law of Electrolysis.

The amount of chemical reaction which occurs at any electrode during electrolysis by a current is proportional to the quantity of electricity passed through the electrolyte.

What is the value of one Faraday ($F$) corresponding to the charge on one mole of electrons?

$96487\,C\,mol^{-1}$ (approximately $96500\,C\,mol^{-1}$).

In a dry cell (Leclanché cell), what reaction occurs at the cathode?

$$MnO_{2} + NH_{4}^{+} + e^{-} \rightarrow MnO(OH) + NH_{3}$$

What are the anode and cathode materials in a lead storage battery?

The anode is lead ($Pb$) and the cathode is a grid of lead packed with lead dioxide ($PbO_{2}$).

What is a fuel cell?

A galvanic cell designed to convert the energy of combustion of fuels like hydrogen, methane, or methanol directly into electrical energy.

In the context of corrosion, into what form are ferrous ions oxidised to create rust?

Hydrated ferric oxide ($Fe_{2}O_{3} \cdot x H_{2}O$).

What is an electrochemical method for preventsing corrosion by using a sacrificial electrode?

Providing a sacrificial electrode of another metal (like $Mg$ or $Zn$) which corrodes itself to save the primary metal object.