Standard Potential

Unlock the secrets of electrochemistry with a dive into Standard Potential, a cornerstone concept that plays a critical role in understanding chemical reactions and processes. This complex topic sits at the crossroads of thermodynamics and redox chemistry, governing the electric potential of a cell under standard conditions. With a grasp of Standard Potential, one can predict the spontaneity of reactions and assess the efficiency of electrochemical cells. The forthcoming sections will meticulously unravel what Standard Potential is, how it is measured, and the various factors influencing its values, equipping readers with the knowledge to navigate this foundational aspect of chemistry with confidence.

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    Understanding Standard Potential in Chemistry

    Grasping the concept of standard potential is pivotal for students who wish to delve into electrochemistry. This measure gives insights into the inherent tendency of chemical species to acquire electrons and thus undergo reduction. Importantly, standard potential values serve as a gateway to predicting the direction of redox reactions and balancing chemical equations.

    What is Standard Potential in Chemistry?

    Standard potential, often represented as E°, is the measure of the electrical potential of a standard electrode against a standard hydrogen electrode, which has been assigned a potential of zero. It is a thermodynamic quantity that indicates how readily an element can gain electrons compared to hydrogen. This value is typically measured under standard conditions, which generally mean at a temperature of 298 K, a pressure of 1 bar, and where all solutions are at 1 molar concentration.

    Standard Potential (E°): The electrochemical potential of a half-cell or full cell under standard conditions, measured relative to the standard hydrogen electrode.

    For instance, if you compare a copper half-cell to a standard hydrogen electrode, the standard potential for copper would be 0.34 volts, denoting that copper is more prone to be reduced than hydrogen.

    Remember, a higher standard potential value indicates a greater tendency for the substance to be reduced.

    Measuring Standard Electrode Half Cell Potentials

    To measure the standard electrode potential of a half-cell, a cell is constructed with the half-cell of interest and a standard hydrogen electrode (SHE). The potential difference between the two is then measured using a voltmeter. It's crucial for the conditions to be maintained at the standard state for accuracy. The standard potential is measured with the half-cell acting as a cathode (reduction taking place) and then as an anode (oxidation occurring) to get a complete understanding of its electrochemical behavior.

    The standard electrode potentials are tabulated and can serve as reference points to deduce the potentials of other half-cells. A table of standard reduction potentials gives the potentials of various half-cells when they are undergoing reduction. It is based on these values that the spontaneity of redox reactions can be calculated using the Nernst equation:

    \[ E = E^\circ - \frac{RT}{nF}\ln Q \]

    Where E is the cell potential, E° is the standard cell potential, R is the gas constant, T is the temperature in Kelvin, n is the number of moles of electrons exchanged in the reaction, F is the Faraday constant, and Q is the reaction quotient.

    To experimentally obtain the standard potential of zinc, for example, connect a zinc electrode to the standard hydrogen electrode, and observe the voltmeter reading which turns out to be -0.76 volts. This indicates that zinc has a lower tendency to gain electrons than hydrogen and is more likely to undergo oxidation.

    A positive standard potential suggests a favorable reduction process, while a negative value implies a stronger inclination for oxidation.

    Factors Affecting Standard Potential Values

    Several factors can influence the standard potential values of substances, which include:

    • Temperature: A change in temperature can shift the balance between the reactants and products in a redox reaction, thus altering the standard potential.
    • Pressure: For gaseous reactants or products, changes in pressure can affect the activity, which in turn can change the standard potential.
    • Concentration: Deviations from the standard 1 molar concentration, particularly in the case of cells involving ions in solution, can result in variations from the listed standard potential values.
    • Nature of the material: The intrinsic properties of the electrode materials, such as their crystalline structure and purity, can have significant effects on their standard potentials.
    • Surface area of the electrodes: Increased surface area can enhance electrode reactions, thus modifying the observed potential.

    Understanding these factors is not only essential for accurate experimental measurements but also for the practical application of electrochemical cells.

    It's interesting to note that the standard potential can be influenced by the physical form of the element in certain cases. For example, different allotropes of carbon like diamond and graphite exhibit different potentials. Moreover, because the standard potential is a thermodynamic property, it's also connected to the Gibbs free energy change. The relationship is defined by the equation:

    \[ \Delta G^\circ = -nFE^\circ \]

    Where \( \Delta G^\circ \) is the change in Gibbs free energy under standard conditions, n is the number of moles of electrons transferred in the half-reaction, and F is the Faraday constant. If \( \Delta G^\circ \) is negative, then the reaction is spontaneous under standard conditions. Conversely, if \( \Delta G^\circ \) is positive, the reaction is non-spontaneous.

    Exploring Examples of Standard Potential

    When studying electrochemical reactions, the standard potential is an essential concept that offers insight into the tendency for a half-cell to either gain or lose electrons. Through exploring examples of standard potential, one can predict whether a certain chemical species will act as an oxidising or reducing agent in a given reaction.

    Common Standard Potentials in Electrochemistry

    In electrochemistry, standard potentials are universally used to predict the direction in which a redox (oxidation-reduction) reaction will proceed. Each half-cell in an electrochemical cell has an inherent standard potential, expressed relative to the standard hydrogen electrode (SHE) potential. To facilitate understanding standard potentials within electrochemistry, reference tables have been created listing the standard potentials of many commonly used half-cells. These tables provide the standard reduction potentials — the voltage observed when the half-cell undergoes reduction at standard conditions of 298 K, 1 bar, and 1 molar concentration.

    Some of the standard potential values for common half-cells include:

    Half CellStandard Potential (V)
    Zn2+/Zn-0.76
    Fe3+/Fe2++0.77
    H2/2H+0 (by definition)
    Cu2+/Cu+0.34
    Ag+/Ag+0.80

    These standard potentials are a fundamental aspect of constructing galvanic cells, where two different metals are connected via an electric circuit. The metal with a lower (more negative) standard potential forms the anode and gets oxidised, while the metal with a higher (more positive) standard potential forms the cathode and gets reduced. Hence, knowing the standard potentials allows chemists to predict the flow of electrons in the circuit.

    The greater the positive value of standard reduction potential, the greater is the element's ability to be reduced and hence act as an oxidising agent.

    Analysing Standard Potential in Everyday Chemical Reactions

    Standard potential is not just an abstract concept confined to textbooks – it has practical implications in everyday chemical reactions. For example, when metals corrode, standard potentials can provide clues about which metals are more likely to be oxidised. In the case of galvanic corrosion, the metal with the more negative standard potential gets oxidised faster. This is crucial in material selection for preventing corrosion in structures and vehicles.In biological systems, the transfer of electrons during cellular respiration and photosynthesis is governed by redox reactions that are influenced by standard potentials. For instance, the electron transport chain consists of a series of compounds with increasing standard potentials, allowing electrons to move spontaneously from one compound to the next, ultimately leading to ATP synthesis.Moreover, standard potentials are used to determine the feasibility of synthesising certain chemical compounds. By comparing the standard potentials of the reactants and products, one can determine whether a given reaction will proceed under standard conditions.

    Consider the reaction between zinc metal and copper sulfate solution: as zinc has a lower standard potential compared to copper, it will undergo oxidation and dissolve, while copper ions will be reduced and plate onto the zinc surface. This can be represented by the reaction:

    Zn(s) + CuSO4(aq) ightarrow ZnSO4(aq) + Cu(s)

    In a battery, the standard potential difference between the anode and cathode directly influences the voltage and energy output of the battery.

    Case Studies: Standard Potential Applications

    Real-world applications of standard potential can be found in various technical and environmental processes. For instance, in the field of environmental science, the standard potential is used to assess the effects of heavy metals in water bodies. Electrodes made of different materials can be used to detect varying concentrations of pollutants by exploiting their standard potentials to catalyse specific reactions.Another illustrative application is in metallurgy where standard potentials guide the electrorefining process. Metals, once extracted from ores, are purified by making them the anodes in electrochemical cells. By selecting a suitable electrolyte and by controlling the cell potential, impurities can be removed as they have different standard potentials compared to the main metal.Energy storage systems such as batteries and fuel cells rely heavily on the knowledge of standard potentials. For rechargeable batteries like lithium-ion, the standard potentials of the chemical components dictate charge-discharge cycles, energy density, and efficiency.

    In the medical field, biosensors often use enzymes that catalyse reactions with well-defined standard potentials. These biosensors can detect the presence of certain molecules, such as glucose, by measuring electrical changes that correspond to the concentration of the analyte. Understanding the standard potential is crucial to designing sensors with high specificity and sensitivity.Moreover, in large-scale industrial electrolysis processes, such as the production of chlorine and sodium hydroxide from brine, standard potentials are central to the design and efficiency calculations. Engineers adjust the cell potential to optimise production rates while minimising energy consumption, thus improving the overall sustainability of the process.

    Navigating the Standard Potential Table

    Familiarising oneself with the standard potential table is a crucial skill in electrochemistry that can facilitate understanding of various redox reactions. The table serves as a conceptual map, guiding chemists to predict the behaviour of half-cells in a reaction. Developing the ability to quickly interpret this table allows for efficient use of these values in calculations and real-world applications.

    Interpreting the Standard Potential Table

    The standard potential table is a comprehensive chart that lists the standard electrode potentials of various redox couples under standard conditions. Each entry on the table usually consists of a half-cell redox reaction and its corresponding standard potential, typically given in volts. To use this table effectively, one must first understand what a redox couple is and the significance of the sign and magnitude of standard potential values.

    A redox couple consists of a reduced form and an oxidised form of a chemical species that can undergo reversible reduction and oxidation. The table lists these half-reactions in order of decreasing potential. The values are measured against the standard hydrogen electrode (SHE), which has been assigned a potential of zero volts. It's also important to note that these potentials are given for the reduction half-reactions. That means the more positive the potential, the greater the tendency of the substance to gain electrons and undergo reduction.

    When navigating the standard potential table, the following points should be considered:

    • Couples are listed with the oxidised form on the left and the reduced form on the right of the half-reaction equation.
    • Standard reduction potentials are reported under standard conditions: 298K (25°C), 1 atm pressure, and 1M concentrations of the aqueous species.
    • The sign of the electrode potential indicates whether the half-reaction is likely to occur spontaneously as a reduction at standard conditions (positive value) or not (negative value).
    • The greater the value of the standard potential, the stronger the oxidising agent.
    • The table can also be used to find the standard potential of the opposite (oxidation) reaction, by changing the sign of the tabulated reduction potential.

    It is essential to be proficient in reading this table to make accurate predictions about electrochemical reactions.

    Standard potential tables often include a line separating the half-cells with positive standard potentials from those with negative potentials, reflecting their respective tendencies to act as oxidising or reducing agents.

    Beyond the basics, the standard potential table also reveals the relative strength of different oxidising and reducing agents. For instance, a common laboratory redox couple is the permanganate ion/manganese (II) ion couple. With a high positive potential, it underscores the strong oxidising power of permanganate in acidic conditions. Conversely, lithium which appears at the very bottom of the table with a highly negative potential, emphasises its reducing strength – why it's used in batteries. In-depth knowledge of these subtleties equips chemists to tailor redox reactions for specific outcomes, such as in synthesis or analytical chemistry.

    To illustrate, when comparing the standard potentials for the Fe3+/Fe2+ (0.771 V) and Ag+/Ag (0.799 V) couples, one can deduce that silver ions are slightly stronger oxidising agents than ferric ions. This could explain why silver ions are effective antimicrobial agents and are used in medical applications.

    How to Use Standard Potential Tables for Predicting Reaction Spontaneity

    Standard potential tables aren't merely for memorisation; they are practical tools for predicting the spontaneity of redox reactions. Understanding how to use these tables to forecast which reactions will occur spontaneously under standard conditions is an essential skill in chemistry. Spontaneous reactions are those that occur without needing an external supply of energy. By examining the standard potentials of the reactants and products, one can deduce whether a reaction is thermodynamically feasible.

    When using standard potential tables in this context, the following steps should be taken:

    • Determine the redox couple of the reactants and their corresponding standard potentials from the table.
    • Do the same for the products of the reaction.
    • Calculate the standard cell potential (E° cell) by subtracting the standard reduction potential of the anode (more negative value) from the potential of the cathode (more positive value):

    \[ E^\circ_\text{cell} = E^\circ_\text{cathode} - E^\circ_\text{anode} \]

    If E° cell is positive, the reaction is thermodynamically favoured and spontaneous under standard conditions. This simple rule underpins the power of the standard potential table for predicting reaction spontaneity.

    In more complex scenarios, when the reactants and products are not in their standard states, the Nernst equation must be employed to calculate the actual cell potential. The Nernst equation takes into consideration the concentrations of the reactants and products as well as the temperature:

    \[ E = E^\circ_\text{cell} - \frac{RT}{nF}ln(Q) \]

    Where E is the actual cell potential, R is the universal gas constant, T is the temperature in kelvins, n is the number of moles of electrons transferred during the reaction, F is the Faraday constant, and Q is the reaction quotient, which is the ratio of concentrations of products to reactants, each raised to the stoichiometric coefficient in the reaction.

    Reaction spontaneity: A measure of whether a chemical reaction will proceed without external energy input under a given set of conditions, mainly determined by the Gibbs free energy change (\( \Delta G \)). If \( \Delta G \) is negative, the process is spontaneous; if positive, it is not.

    Consider the reaction:

    Zn(s) + Cu2+(aq) ightarrow Zn2+(aq) + Cu(s)

    To predict if this reaction will occur spontaneously. The standard potential for the Zn2+/Zn couple is -0.76 V, and for Cu2+/Cu, it’s +0.34 V. Therefore:

    \[ E^\circ_\text{cell} = (+0.34 V) - (-0.76 V) = +1.10 V \]

    This positive E° cell indicates that the reaction should be spontaneous under standard conditions.

    Keep in mind that a spontaneous reaction may not proceed at a noticeable rate; kinetics are also a crucial factor for evaluating whether a reaction will practically occur.

    An interesting application of the standard potential table in predicting spontaneity is in redox flow batteries, where two solutions of different redox couples are pumped through an electrochemical cell. By choosing redox couples with a significant difference in standard potential, these batteries can store and deliver large amounts of energy efficiently. Engineers must account for the spontaneity of these redox reactions when designing the system, ensuring that the battery can charge and discharge repeatedly with high efficiency and minimal degradation over time.

    The Standard Potential Equation Explained

    The standard potential equation is a fundamental concept in electrochemistry that allows you to quantify the tendency of a redox (reduction-oxidation) system to lose or gain electrons. This equation aids in the comprehension of the driving force behind chemical reactions and their spontaneous nature under standard conditions. By mastering the standard potential equation, you can predict the outcome of electrochemical cells and harness this knowledge for practical applications like battery design or corrosion prevention.

    Mathematical Representation of Standard Potential

    Standard potential, denoted by E°, is the voltage associated with a reduction or oxidation reaction when all reactants and products are in their standard states – typically 1 mol/L concentration, at 1 atmosphere of pressure, and 25°C (298K). This property is measured relative to the standard hydrogen electrode (SHE), which is arbitrarily set at zero volts. The mathematical representation of standard potential is critical because it binds together various concepts like electrode potential and thermodynamics.

    For an electrochemical cell comprising two half-cells, the standard cell potential (E°cell) is expressed as the difference in potential between the cathode and the anode. Mathematically, it is represented as:

    \[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \]

    Each half-cell potential is determined under standard conditions and tabulated as standard reduction potentials. These tabulated values are referenced to ascertain the electrode potentials for various redox pairs. It's important to note that standard potentials are typically presented as reduction potentials, meaning for the half-reaction to gain electrons. To determine the oxidation potential, simply reverse the sign of the standard reduction potential. In thermodynamics, this potential is tied to the Gibbs free energy change (\( \Delta G^\circ \)) of the reaction through the equation:

    \[ \Delta G^\circ = -nFE^\circ \]

    Where \( n \) is the number of moles of electrons transferred in the redox reaction, \( F \) is the Faraday constant (approximately 96485 C/mol), and \( E^\circ \) is the standard cell potential. A negative Gibbs free energy change indicates that the reaction can occur spontaneously under standard conditions.

    Standard Hydrogen Electrode (SHE): A reference electrode with an assigned standard potential of 0 V against which the potential of all other electrodes is measured.

    Standard Reduction Potential: The potential at which a species gains electrons (is reduced) when all components are in their standard states.

    As an example of calculating the standard cell potential, consider a cell made of a zinc electrode (Zn/Zn2+, standard potential -0.76 V) and a copper electrode (Cu/Cu2+, standard potential +0.34 V). The standard cell potential would be calculated as:

    \[ E^\circ_{\text{cell}} = E^\circ_{\text{Cu/Cu^{2+}}} - E^\circ_{\text{Zn/Zn^{2+}}} \]

    \[ E^\circ_{\text{cell}} = (+0.34 \text{ V}) - (-0.76 \text{ V}) = +1.10 \text{ V} \]

    Remember to check the sign when calculating anode and cathode potentials; anodes typically have a negative standard potential, while cathodes have a positive one.

    Calculations Involving the Standard Potential Equation

    Utilizing calculations involving the standard potential equation allows you to predict the feasibility and direction of redox reactions. The standard cell potential (E°cell) forms the basis for determining whether a redox reaction will occur spontaneously under standard conditions. You can also use the standard potentials to calculate the actual potential at non-standard conditions using the Nernst equation. This equation adjusts the standard potential for the effect of concentration, pressure, and temperature.

    The Nernst equation is expressed as:

    \[ E = E^\circ - \frac{RT}{nF}\ln(Q) \]

    Where:

    • R is the universal gas constant (8.314 J/(mol·K))
    • T is the temperature in Kelvin (K)
    • n is the number of moles of electrons transferred in the electrochemical reaction
    • F is the Faraday constant (approximately 96485 C/mol)
    • Q is the reaction quotient which is a ratio of the activity of the products to the reactants, raised to the power of their stoichiometric coefficients in the balanced chemical equation

    Likewise, standard potentials are pivotal in calculating the electromotive force (EMF) of a cell, which is the force driving electrons around a circuit. The EMF of an electrochemical cell is simply its cell potential under open-circuit conditions.

    When calculating cell potential for non-standard conditions, it's imperative to remember that concentration, expressed as activity, plays a crucial role. The unit term for solids and liquids is essentially '1', reflecting their pure states. This leads to simplifications when solids or liquids are involved in the redox reaction, as their contributions to Q are effectively negated in the Nernst equation.

    Another consideration pertains to electrochemical series which helps to predict the direction of electron flow in a galvanic cell. A half-cell with a higher standard potential will naturally draw electrons towards itself, thus acting as the cathode, while the half-cell with a lower standard potential will act as the anode.

    Gibbs Free Energy Change (\( \Delta G \)): A thermodynamic property indicating the spontaneity of a reaction; a negative value means the reaction is spontaneous, while a positive value indicates that energy input is required for the reaction to proceed.

    To illustrate the use of the Nernst equation in electrochemical cells, let’s look at the cell potential for the same zinc-copper cell at non-standard conditions. Let's consider concentrations of 0.01 M Cu2+ and 1 M Zn2+ at 298 K:

    \[ Q = \frac{[\text{Cu}^{2+}]}{[\text{Zn}^{2+}]} = \frac{0.01}{1} \]

    \[ E = E^\circ_{\text{cell}} - \frac{(8.314)(298)}{(2)(96485)}\ln(0.01) \]

    \[ E = 1.10 - \frac{(8.314)(298)}{(2)(96485)}\ln(0.01) \]

    \[ E \approx 1.16 V \]

    This result indicates that the actual potential increases when the concentration of the cathodic solution decreases, compared to the standard cell potential.

    While the standard potential is independent of concentration, the actual potential measured, as described by the Nernst equation, takes into consideration any deviations in reactant and product concentrations from 1 M.

    Standard Potential in Aqueous Solutions

    Standard potential in aqueous solutions is a fundamental parameter in electrochemistry that offers a comparison of the relative tendencies of different solutes to undergo oxidation or reduction. It is intrinsically linked to the activity of the ions in solution, which in turn is influenced by the properties of the solvent. Understanding standard potential in aqueous solutions is imperative for designing batteries, predicting corrosion, and many other applications in both industrial processes and research.

    Influence of Solvent on Standard Potential Values

    The influence of the solvent, such as water in aqueous solutions, on standard potential values is notable due to the solvent's role in solvating ions and influencing their activities. The standard potential is fundamentally an intensive property, meaning it does not depend on the amount of substance but can vary with the choice of solvent. The dielectric constant of the solvent, the ionic strength of the solution, and specific solvation effects can cause shifts in the standard potentials. Water, with its high dielectric constant, stabilises the charge of ions in solution and affects the standard potential listed for aqueous systems. The hydration shell that forms around ions changes their apparent size, altering transport properties and reactivity.

    Factors like the pH of the solution and the presence of complexing agents can also alter the activity of ions and, hence, the standard potential. Solvent properties impact electrostatic interactions between ions, which subsequently affect the electrical double layer at the electrode-solution interface. Sometimes, when the solvent itself can get oxidised or reduced at the electrode surface, this will have a profound impact on the measurable standard potential.

    Consider the standard potential of silver ion reduction:

    \[ \text{Ag}^{+}(aq) + \text{e}^{-} \rightarrow \text{Ag}(s) \]

    In water, the standard potential for this reaction is +0.80 V. However, in a solvent like acetonitrile, with different solvation capabilities and a lower dielectric constant than water, the potential value could differ significantly.

    It is crucial to recognise that temperature and pressure, as parts of the standard state conditions which normally are 1 atm and 298 K respectively, may also influence solvent characteristics, leading to potential variations.

    To illustrate the influence of solvent on standard potential, let's compare the reduction of the ferric ion to the ferrous ion in two different solvents: water and methanol.

    Water:

    \[ \text{Fe}^{3+}(aq) + \text{e}^{-} \rightarrow \text{Fe}^{2+}(aq), \quad E^{\circ} = +0.77 \text{V} \]

    Methanol:

    \[ \text{Fe}^{3+}(sol) + \text{e}^{-} \rightarrow \text{Fe}^{2+}(sol), \quad E^{\circ} \text{ may differ from } +0.77 \text{V} \]

    Where 'sol' denotes methanol as solvent. The change in potential evidences how solvent properties like dielectric constant and solvation energy influence ion activities and the resulting redox behaviour.

    When working with solutions other than water, one should consider the non-aqueous standard potentials, which may be significantly different from the aqueous values.

    Additional intricacies include the solvation numbers and the specific ion pair formation in solvents other than water. For example, in solvents with low dielectric constants, the tendency for ions to pair up is higher, which could drastically affect the standard potential. The Born-Haber cycle is often utilised in theoretical chemistry to estimate how differences in solvation energies can impact ionic activities and standard potentials in various solvents.

    Practical Examples of Standard Potential in Aqueous Solutions

    Aqueous solutions are ubiquitous in chemistry, and the standard potentials of solutes in these solutions have many practical applications. These applications range from the creation of electrochemical cells in batteries to the prediction of reaction outcomes in biochemical systems. For instance, the reduction potential of oxygen in water is a key component in calculating the energy output of a fuel cell. Similarly, the standard potential is used to determine the electrochemical series, which ranks metals based on their tendency to oxidise. This is crucial in metallurgy and corrosion science, where metals are selected based on resistance to oxidation, informed by their positions in this series.

    In environmental chemistry, the redox potential of contaminants helps assess their behaviour and potential impact on water bodies. The remediation techniques for these contaminants can then be developed accordingly. Standard potentials are also relevant in pharmaceuticals, where redox chemistry determines the stability and reactivity of active pharmaceutical ingredients.

    Another significant application area is in analytical chemistry. Techniques like cyclic voltammetry use standard potential to determine electroactive species' concentration in a solution. It is based on the relation that the peak current in cyclic voltammetry is proportional to the concentration of the species of interest.

    Lastly, the very bases of life, such as cellular respiration and photosynthesis, are redox processes governed by the standard potentials of various participants. It’s the gradient in standard potentials across the mitochondrial membrane that enables ATP synthesis, driving the energy production in cells.

    Consider the Daniell cell, a classic example of an electrochemical cell, which consists of a zinc electrode in a zinc sulfate solution and a copper electrode in a copper sulfate solution. The zinc electrode serves as the anode with the following half-reaction:

    \[ \text{Zn}(s) \rightarrow \text{Zn}^{2+}(aq) + 2\text{e}^{-}, \quad E^{\circ}_{\text{anode}} = -0.76 \text{V} \]

    And the copper electrode acts as the cathode with this reaction:

    \[ \text{Cu}^{2+}(aq) + 2\text{e}^{-} \rightarrow \text{Cu}(s),\quad E^{\circ}_{\text{cathode}} = +0.34 \text{V} \]

    The cell potential, calculated from the standard potentials, predicts that electrons will flow from zinc to copper, which can be visually confirmed by the deposition of copper on the zinc electrode.

    Many common batteries, such as alkaline and lead-acid batteries, operate based on the principles of standard potentials in aqueous solutions.

    Standard Potential - Key takeaways

    • Standard Potential (E°): A thermodynamic measure of the electrical potential of a standard electrode against a standard hydrogen electrode under standard conditions (298 K, 1 bar, 1 molar concentration).
    • Standard Hydrogen Electrode (SHE): A reference electrode with an assigned potential of 0 V, used for measuring standard electrode half-cell potentials.
    • Standard Electrode Half Cell Potentials: Tabulated values that represent how readily elements undergo reduction compared to hydrogen; used to predict redox reaction directions and spontaneity.
    • Standard Potential Equation: Expressed as E = E° - (RT/nF)ln Q, to calculate cell potential under non-standard conditions, where R is the gas constant, T is temperature in Kelvin, n is the number of moles of electrons exchanged, F is the Faraday constant, and Q is the reaction quotient.
    • Influence of Solvent on Standard Potential: Properties of the solvent, such as the dielectric constant and solvation effects, can affect the standard potential in aqueous solutions, crucial for applications in electrochemistry.
    Frequently Asked Questions about Standard Potential
    What factors influence the standard potential of an electrode in electrochemistry?
    The standard potential of an electrode in electrochemistry is influenced by the nature of the metal, the temperature, the concentration of ions in the solution, and the pressure of gases involved in the electrode reactions.
    How can one calculate the standard cell potential from standard electrode potentials?
    To calculate the standard cell potential (E°cell), subtract the standard electrode potential (E°) of the anode (negative electrode) from the standard electrode potential of the cathode (positive electrode): E°cell = E°cathode - E°anode.
    What is the significance of a negative standard potential in electrochemical series?
    A negative standard potential in the electrochemical series signifies that the species is a stronger reducing agent than the hydrogen electrode, indicating its tendency to lose electrons and undergo oxidation more readily.
    What is the difference between standard potential and actual measured electrode potential?
    The standard potential is a theoretical value based on conditions of 1 molar concentration, a pressure of 1 atmosphere, and a temperature of 298 K (25°C), whereas the actual measured electrode potential is the voltage observed under specific, often non-standard, experimental conditions.
    How does temperature affect the standard electrode potential in electrochemical reactions?
    Temperature changes can affect the kinetics of electrochemical reactions, potentially shifting the standard electrode potential. An increase in temperature generally increases reaction rates, potentially leading to a more positive standard potential for endothermic reactions and a more negative potential for exothermic reactions due to the Nernst equation.

    Test your knowledge with multiple choice flashcards

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