ABC/123 Version X Week 4 Exercises CHM/109 Version Univers

ABC/123 Version X 1 Week 4 Exercises CHM/109 Version University of

Prepare written answers to the following exercises:

Paper For Above instruction

1. Identification of Elements Likely to Form Oxides in Soil Samples

As an environmental scientist collaborating with a chemist, the analysis of soil samples through mass spectrometry revealed the presence of four elements: Selenium (Se), Tin (Sn), Lead (Pb), and Cadmium (Cd). To determine which of these elements are likely to form oxides in the environment, we analyze their electronic configurations, valence electrons, and ionization energies, factors that influence their bonding tendencies and oxide formation.

Electron configurations provide insight into the number of valence electrons, which are primarily responsible for an element's chemical reactivity, especially in oxidation reactions. The electron configurations of the elements are as follows:

• Selenium (Se): [Ar] 3d¹⁰ 4s² 4p⁴
• Tin (Sn): [Kr] 4d¹⁰ 5s² 5p²
• Lead (Pb): [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p²
• Cadmium (Cd): [Kr] 4d¹⁰ 5s²

Valence electrons are determined from the outermost electrons in the electron configurations:

• Selenium: 6 valence electrons (4p⁴)
• Tin: 4 valence electrons (5s² 5p²)
• Lead: 4 valence electrons (6s² 6p²)
• Cadmium: 2 valence electrons (5s²)

Ionization energy trends are crucial; lower ionization energy indicates a greater tendency to lose electrons and form positive ions, which readily combine with oxygen to form oxides. Jurisdiction of ionization energies, from lowest to highest, based on periodic trends, approximately:

1. Lead (Pb): lowest ionization energy among the four, thus most likely to form oxides
2. Cadmium (Cd)
3. Tin (Sn)
4. Selenium (Se): highest ionization energy, less likely to form oxides directly with oxygen in this oxidation state

Based on the valence electrons and ionization energy trends, both selenium and tin are known to form stable oxides, such as SeO₂ or SeO₃, SnO and SnO₂. Lead readily forms PbO and PbO₂. Cadmium also forms CdO, though less commonly with complex oxide forms. Given these trends, the elements most likely to form oxides in the soil are Se, Sn, and Pb, with Cadmium being less reactive in oxide formation but still capable.

2. Molecular Geometry and Lewis Structures of Compounds in Enzyme Inhibition

Understanding the shape of molecules is vital for predicting how they interact with enzyme active sites. The molecules under consideration are CO₂, KOH, NO₃, and HCN. Drawing Lewis structures facilitates determination of their molecular geometries based on VSEPR theory.

Carbon Dioxide (CO₂)

The Lewis structure features a carbon atom double-bonded to two oxygen atoms. The molecule is linear with a bond angle of approximately 180°, due to the two double bonds and no lone pairs on carbon.

Potassium Hydroxide (KOH)

In KOH, potassium (K⁺) is the cation, and the hydroxide ion (OH^-) exhibits a bent geometry with a bond angle near 104.5°, owing to the lone pairs on oxygen. The molecule as a whole is ionic, with the K⁺ ion and the hydroxide ion interacting through electrostatic attraction.

Nitrate Ion (NO₃^-)

The Lewis structure shows a nitrogen atom centrally bonded to three oxygen atoms with one of these bonds bearing a negative formal charge. Resonance structures distribute the negative charge over the oxygens, leading to a trigonal planar shape with bond angles approximately 120°.

Hydrogen Cyanide (HCN)

Structurally, HCN has a triple bond between carbon and nitrogen, with hydrogen bonded to carbon. The molecular geometry around carbon is linear, with bond angles of 180°, facilitating its small, linear shape critical for fitting into enzyme active sites.

These molecular geometries suggest that molecules with linear structures, such as CO₂ and HCN, are more likely to fit into the enzyme’s pocket if geometry compatibility is a key factor. The bent structure of OH^- and resonance structures of NO₃^- influence their reactivity and binding interactions but generally do not fit as neatly into linear enzyme pockets unless specifically designed for such shape complementarity.

3. Identification and Classification of Compounds in Battery Manufacturing

Understanding the nature of compounds used in batteries requires identification of each substance’s chemical formula, name, and whether it is ionic or molecular—important for their ability to generate ions in aqueous solutions.

• PtO₂: Platinum(IV) oxide; molecular compound, as it consists of a metal and oxygen atoms bonded covalently
• CF₂Cl₂: Dichlorodifluoromethane; molecular compound, with covalent bonds between C, F, and Cl atoms
• CO: Carbon monoxide; molecular, with a covalent triple bond between C and O
• KClO₃: Potassium chlorate; ionic, with K⁺ cation and ClO₃^- anion
• CoSO₄: Cobalt(II) sulfate; ionic, composed of Co²⁺ and SO₄^2-
• CO₂: Carbon dioxide; molecular, with covalent double bonds
• SO₃: Sulfur trioxide; molecular, covalent bonds in a trigonal planar shape
• Ba(NO₃)₂: Barium nitrate; ionic, with Ba²⁺ cation and NO₃^- ions
• NH₄I: Ammonium iodide; ionic, with NH₄⁺ and I^-
• NaClO₄: Sodium perchlorate; ionic, with Na⁺ and ClO₄^-

In summary, compounds such as PtO₂ and CO are molecular, while KClO₃, CoSO₄, Ba(NO₃)₂, NH₄I, and NaClO₄ are ionic, facilitating ion production essential for battery operation.

Conclusion

Understanding the chemical and geometric properties of elements and compounds is vital across different fields such as environmental science, biochemistry, and energy technology. By analyzing electronic configurations and molecular geometries, scientists can predict reactivity, binding affinity, and functional behavior, guiding practical applications and innovations. Recognizing whether compounds are ionic or molecular further influences their utility, especially in devices like batteries where ion generation and transfer are fundamental.

References

• Brown, T. L., LeMay, H. E., Bursten, B. E., Murphy, C., & Woodward, J. (2018). Chemistry: The Central Science (14th ed.). Pearson.
• Petrucci, R. H., Herring, F. G., Madura, J. D., & Bissonnette, C. (2017). General Chemistry: Principles & Modern Applications (11th ed.). Pearson.
• Tro, N. J. (2018). Chemistry: A Molecular Approach (4th ed.). Pearson.
• Housecroft, C. E., & Sharpe, A. G. (2018). Inorganic Chemistry (5th ed.). Pearson.
• Huheey, J. E., Keiter, E. A., & Keiter, R. L. (2012). Inorganic Chemistry: Principles of Structure and Reactivity (4th ed.). Pearson.
• Zumdahl, S. S., & Zumdahl, S. A. (2014). Chemistry (9th ed.). Cengage Learning.
• Atkins, P., & de Paula, J. (2018). Physical Chemistry (11th ed.). Oxford University Press.
• Lehninger, A. L., Nelson, D. L., & Cox, M. M. (2017). Lehninger Principles of Biochemistry (7th ed.). W.H. Freeman.
• McMurry, J., & Fay, R. C. (2019). Organic Chemistry (10th ed.). Cengage Learning.
• Chang, R., & Goldsby, K. (2016). Chemistry (13th ed.). McGraw-Hill Education.