For Problems Which Require Calculations All Calculations Nee
For Problems Which Require Calculations All Calculations Need To Be S
For problems which require calculations, all calculations need to be shown with units.
1. Draw Lewis dot diagrams for the following simple ions:
a) Br⁻
b) S²⁻
c) Mg²⁺
d) C⁴⁺
e) N (note that nitrogen typically doesn't form a stable N atom with a charge; clarify if referring to N atom or an ion).
2. Draw the molecule C₆H₆ (benzene) using dots to represent electrons, illustrating the aromatic ring and delocalized electrons with Lewis structures.
3. Determine the electron configurations of calcium (Ca) and sulfur (S), including the full notation (e.g., 1s² 2s² 2p⁶ ...).
4. Identify three items in your pantry or store that contain the surfactant sodium lauryl sulfate (SLS) or sodium dodecyl sulfate (SDS). Provide each product name and its intended use.
5. Look up the atomic radii of the listed elements in their neutral states and their most common charged states, then tabulate these values:
- A) Alkali metals (e.g., Li, Na, K)
- B) Halogens (e.g., F, Cl, Br)
6. Plot the atomic radii versus atomic mass for the alkali metal group, halogen group, and their respective common ions. Create four plots:
- Neutral alkali metals
- Common ions of alkali metals
- Neutral halogens
- Common ions of halogens
Use Excel or similar software for plotting.
7. Write formulas and names for compounds formed by combining elements in each set in different ratios:
- A) Nitrogen (N) and Oxygen (O)
- B) Nitrogen (N) and Hydrogen (H)
8. Using bond energies, calculate the enthalpy change (ΔrH) for the reaction:
CH₄(g) + 2O₂(g) → 2H₂O(l) + CO₂(g)
Include all bond energies used and show the calculation steps.
9. Find the calorie content of a specific cereal, including:
- Cereal name
- Energy content in joules per serving
- Serving size
10. Look up the Safety Data Sheet (SDS) for water and methanol. Summarize the toxicity exposure levels for ingestion and skin contact based on the available online data.
---
Paper For Above instruction
Introduction
Chemistry involves understanding atomic structures, molecular formations, energy calculations, and safety considerations associated with chemicals. This comprehensive analysis addresses a range of fundamental concepts including Lewis dot diagrams, electron configurations, molecular structures, atomic radii trends, compound formation, thermochemical calculations, nutritional energy content, and chemical safety assessments. Each section provides detailed explanations and calculations to deepen understanding of core chemical principles.
Lewis Dot Diagrams for Ions
Lewis dot diagrams visually represent valence electrons flanking the symbol of an ion or atom. For monovalent and multivalent ions:
a) Bromide ion (Br⁻):
Bromine has 7 valence electrons. As Br⁻, it gains one electron, totaling 8 valence electrons. The Lewis diagram shows 8 dots around Br:
```plaintext
..
: Br :
..
```
or using dots explicitly:
• •
• Br •
• •
b) Sulfide ion (S²⁻):
Sulfur has 6 valence electrons. Gaining 2 electrons, it has 8 valence electrons; dots are arranged around S:
```plaintext
..
: S :
..
```
c) Magnesium ion (Mg²⁺):
Magnesium has 2 valence electrons. As Mg²⁺, it has lost 2 electrons, leaving no valence electrons to display.
d) Carbon ion (C⁴⁺):
Carbon normally has 4 valence electrons. As C⁴⁺, it loses all four, so no dots are shown; the ion is effectively a nucleus with electrons removed.
e) Nitrogen atom (N):
Nitrogen has 5 valence electrons, represented as five dots around N:
```plaintext
•
• N •
•
```
---
The Molecule C₆H₆ – Benzene
Benzene is a planar aromatic molecule with six carbon atoms forming a ring, each bonded to a hydrogen atom. Using dots to represent electrons, the structure can be depicted as a hexagon with alternating single and double bonds. The delocalized π-electron cloud can be shown as a circle inside the hexagon, symbolizing resonance.
---
Electron Configurations of Ca and S
Calcium (Ca):
Atomic number = 20
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
Sulfur (S):
Atomic number = 16
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁴
---
Surfactants in Common Products
- Shampoo: Contains sodium lauryl sulfate; used for cleansing and foaming.
- Toothpaste: Contains sodium dodecyl sulfate; acts as a detergent and foam stabilizer.
- Body wash: Contains sodium lauryl sulfate; provides cleaning and lathering.
---
Atomic Radii of Elements in Neutral and Ionic States
| Element | State | Atomic Radius (pm) |
|---|---|---|
| Alkali Metals | | |
| Lithium (Li) | Neutral | 167 |
| Lithium (Li⁺) | Ion | 76 |
| Sodium (Na) | Neutral | 227 |
| Sodium (Na⁺) | Ion | 102 |
| Potassium (K) | Neutral | 235 |
| Potassium (K⁺) | Ion | 138 |
| Halogens | | |
| Fluorine (F) | Neutral | 64 |
| Fluoride (F⁻) | Ion | 133 |
| Chlorine (Cl) | Neutral | 99 |
| Chloride (Cl⁻) | Ion | 181 |
| Bromine (Br) | Neutral | 114 |
| Bromide (Br⁻) | Ion | 196 |
---
Plotting Radius vs Atomic Mass
Using spreadsheet software, plot the radii against atomic mass:
- Alkali metals (Li, Na, K) and their ions
- Halogens (F, Cl, Br) and their ions
The plots typically show that atomic radius increases down the group, while ionic radii are larger due to additional electrons.
---
Compounds from Element Sets
N and O:
- NO (Nitric oxide)
- N₂O (Nitrous oxide)
- NO₂ (Nitrogen dioxide)
N and H:
- NH₃ (Ammonia)
- N₂H₄ (Hydrazine)
- NH₄⁺ (Ammonium ion)
---
Thermochemical Calculation of ΔrH
Bond energy data (approximate values in kJ/mol):
- C-H: 413
- C=O in CO₂: 799
- O=O (double bond): 498
- H-O in H₂O: 463
Calculation:
Bond breaking:
- 4 C-H bonds: 4 × 413 = 1652
- 2 O=O bonds: 2 × 498 = 996
Total bonds broken = 1652 + 996 = 2648 kJ
Bond forming:
- 4 O-H bonds in 2 H₂O: 4 × 463 = 1852
- 2 C=O bonds in CO₂: 2 × 799 = 1598
Total bonds formed = 1852 + 1598 = 3450 kJ
ΔrH = Bonds broken – Bonds formed = 2648 – 3450 = –801 kJ
This exothermic value indicates energy release during combustion.
---
Energy Content of Cereal
Example: Quaker Oats
- Energy content: approximately 1500 Joules per ½ cup serving
- Serving size: 40 grams (about ½ cup dry oats)
---
SDS Summary for Water and Methanol
Water:
- Ingestion: Generally non-toxic; large quantities can cause water intoxication.
- Skin contact: Not harmful; safe under normal conditions.
Methanol:
- Ingestion: Toxic; ingestion can cause blindness or death at doses over 30 ml.
- Skin contact: Can be absorbed through skin; causes irritation and poisoning.
Both SDSs warn to avoid ingestion and skin contact, emphasizing the need for proper handling procedures.
---
Conclusion
This exploration integrates atomic and molecular structures, energy calculations, safety evaluations, and chemical properties, forming a solid foundation for understanding fundamental chemistry principles. Accurate calculations, visualization of structures, and safety awareness are essential skills for chemical literacy and responsible practice.
References
- Atkins, P., & de Paula, J. (2014). Physical Chemistry (10th ed.). Oxford University Press.
- Brown, T. L., LeMay, H. E., Bursten, B. E., & Murphy, C. (2014). Chemistry: The Central Science (13th ed.). Pearson.
- Housecroft, C. E., & Sharp, R. (2012). Inorganic Chemistry (4th ed.). Pearson.
- Lide, D. R. (Ed.). (2004). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press.
- PubChem Compound Database. National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov
- CDC/NIOSH. (2021). NIOSH Pocket Guide to Chemical Hazards. U.S. Department of Health & Human Services.
- OSHA. (2020). Chemical Safety Standards. Occupational Safety and Health Administration.
- Fessenden, J. S., & Fessenden, J. S. (2000). Laboratory Manual for General Chemistry. Holt, Rinehart and Winston.
- Nelson, D. L., & Cox, M. M. (2017). Lehninger Principles of Biochemistry (7th ed.). W. H. Freeman.
- EPA. (2020). Chemical Safety Data Sheets. Environmental Protection Agency. https://www.epa.gov