Electrode Potentials and Oxidizing Reactions

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Questions and Answers

What trend is observed in the standard electrode potentials for the elements Ti to Zn?

An increase in negative E values.

A decrease in the first and second ionisation enthalpies.

Less negative E values related to increased ionisation enthalpies. (correct)

E values show no pattern across the elements.

Why is Cr2+ considered a reducing agent?

Both Cr2+ and Mn3+ are equally reducing.

Due to the transition to a half-filled t2g level configuration. (correct)

It has a high ionisation energy.

Because d4 configuration is unstable.

What characteristic of Mn3+ makes it an oxidizing agent?

It has a positive standard electrode potential.

It has a d5 configuration which is less stable.

Mn3+ has a higher ionisation energy than Mn2+.

It transitions to a stable half-filled d5 configuration. (correct)

What is the standard electrode potential (E) for the transformation of copper (Cu) as stated?

Positive +0.34 V. Signup and view all the answers

What does a positive E value imply about a substance, considering the case of copper?

It has a high standard enthalpy change (∆aH) and low hydration enthalpy (∆hydH). Signup and view all the answers

What role does manganese(II) ions play in the oxidation reaction of permanganate?

They speed up the reaction. Signup and view all the answers

What is the product formed when iodine is liberated from potassium iodide in an acidic solution?

I2 Signup and view all the answers

When oxalic acid is oxidized by permanganate at 333 K, which gas is produced?

CO2 Signup and view all the answers

What does hydrogen sulfide get oxidized to in the presence of permanganate?

S Signup and view all the answers

Which of the following species is formed when nitrite is oxidized by permanganate?

Nitrate Signup and view all the answers

Which element has the highest E value in the provided data?

Zn Signup and view all the answers

What is the significance of the d sub-shell configurations in Mn and Zn?

They indicate stability in half-filled and completely filled configurations. Signup and view all the answers

What is the E value for Cu in the data provided?

0.34 Signup and view all the answers

Which metal has the lowest energy value, indicating stronger stability for its configuration?

Fe Signup and view all the answers

What trend can be observed in the E values for the transition metals listed?

E values vary significantly based on the d configurations. Signup and view all the answers

What does a high negative ∆hydH indicate for an element?

Strong reducing capability. Signup and view all the answers

Which metal's E value is most directly associated with its stable noble gas configuration?

Sc Signup and view all the answers

How is the E for Ni significant compared to its transition metal counterparts?

It is influenced by the highest negative ∆hydH. Signup and view all the answers

What trend is observed in the hardness of the lanthanoids with increasing atomic number?

Hardness increases with increasing atomic number. Signup and view all the answers

Which of the following lanthanoids has the highest melting point?

Samarium Signup and view all the answers

Which ions among the lanthanoids do not show any color in solid state or aqueous solutions?

Lutetium and Lanthanum Signup and view all the answers

What is the general chemical behavior trend of the lanthanoids as atomic number increases?

They become less reactive and behave more like aluminium. Signup and view all the answers

What phenomenon is attributed to the color of many trivalent lanthanoid ions?

Excitation of f electrons. Signup and view all the answers

What is the approximate first ionisation enthalpy of lanthanoids?

Around 600 kJ mol⁻¹ Signup and view all the answers

Which statement best describes the third ionisation enthalpy variations among lanthanoids?

Certain orbitals exhibit stability affecting their values. Signup and view all the answers

Which lanthanoid is noted for having an abnormally low value of third ionisation enthalpy?

Lanthanum Signup and view all the answers

What is produced when iodide is oxidised in faintly alkaline solutions?

Iodate Signup and view all the answers

What does thiosulphate convert into during oxidation in neutral solutions?

Sulfate Signup and view all the answers

Which of the following elements serves as a catalyst for the oxidation of manganous salt?

Zinc Signup and view all the answers

Which acidic condition is unsatisfactory for permanganate titrations?

Hydrochloric acid Signup and view all the answers

What is a common application of potassium permanganate in preparative organic chemistry?

Bleaching agent Signup and view all the answers

Which series of elements is referred to as the lanthanoids?

Elements following lanthanum Signup and view all the answers

What general symbol is often used to represent the lanthanoids?

Ln Signup and view all the answers

How many elements are included in the actinoid series?

14 Signup and view all the answers

Study Notes

Standard Electrode Potential Trends

The general trend of less negative E values is related to the increasing sum of first and second ionization enthalpies.
Manganese, nickel, and zinc have more negative E values than expected, deviating from the trend.
Chromium(II) is reducing because its configuration changes from d⁴ to d³, achieving a half-filled t₂g level.
Manganese(III) is oxidizing because its configuration changes from d⁴ to d⁵, resulting in a half-filled d shell, which is more stable.

Thermochemical Data and Electrode Potentials

The table shows relationships between thermodynamic properties and E values.
A higher negative enthalpy of hydration (∆hydH) for nickel contributes to its negative E value.
Stability of the half-filled d⁵ subshell in Mn and the completely filled d¹⁰ configuration in Zn contribute to their respective E values.

Important Oxidising Reactions of KMnO₄ in Acid Solutions

Potassium permanganate (KMnO₄) is a strong oxidant capable of oxidizing several substances in acidic solutions.
KMnO₄ oxidizes iodide to iodine, Fe²⁺ to Fe³⁺, oxalate ion or oxalic acid to carbon dioxide, hydrogen sulfide to sulfur, sulfurous acid or sulphite to sulfate or sulfuric acid, and nitrite to nitrate.

Important Oxidising Reactions of KMnO₄ in Neutral or Faintly Alkaline Solutions

KMnO₄ oxidizes iodide to iodate, thiosulphate to sulphate, and manganous salt to MnO₂ in neutral or faintly alkaline solutions.

Uses of KMnO₄

Potassium permanganate (KMnO₄) is used in analytical chemistry, preparative organic chemistry, as a bleach for textiles, and for decolorization in oils.

Inner Transition Elements: Lanthanoids and Actinoids

Lanthanoids (Ln) and Actinoids are the two series of f-block elements, following Lanthanum and Actinium, respectively.
Lanthanoids are more similar to each other than other transition metals due to their similar oxidation states.
Actinoid chemistry is more complex than that of lanthanoids.

Characteristics of Lanthanoids

Hardness increases with atomic number, with samarium being steel hard.
Melting points range between 1000 to 1200 K, except for samarium which melts at 1623 K.
Lanthanoids have metallic structures, are good conductors of heat and electricity, and exhibit smooth changes in density and properties, except for Eu and Yb.
Trivalent lanthanoid ions are often colored, attributed to the presence of f electrons.
Lanthanoid ions are paramagnetic, except for f⁰ (La and Ce) and f¹⁴ (Yb and Lu) type ions.

Electronic Configuration and Ionization Enthalpies of Lanthanoids

First ionization enthalpies of lanthanoids are around 600 kJ mol⁻¹, and the second is about 1200 kJ mol⁻¹, comparable to calcium.
The third ionization enthalpy shows variation due to the exchange enthalpy considerations, leading to stability for empty, half-filled and completely filled f orbitals.
This is indicated by abnormally low third ionization enthalpy values for lanthanum, gadolinium, and lutetium.

Chemical Reactivity of Lanthanoids

The earlier members of the lanthanoid series are highly reactive, similar to calcium, but reactivity decreases as atomic number increases.
With increasing atomic number, lanthanoids exhibit more similarities to aluminum.

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Description

This quiz explores the trends in standard electrode potentials and their thermochemical data, focusing on specific elements like manganese, nickel, and zinc. It also covers important oxidizing reactions of potassium permanganate in acid solutions. Test your knowledge on the relationships between ionization enthalpies and electrode potentials.