Intro to Chemistry Exam 2 Study Guide & Practice Problems

Q1. Naming Compounds

Background

Topic: Chemical Nomenclature

This section tests your ability to apply naming rules for ionic and covalent compounds using the periodic table and naming conventions.

Key Terms and Concepts:

• Ionic compounds: Metal + nonmetal, use Roman numerals for transition metals.

• Covalent compounds: Nonmetal + nonmetal, use Greek prefixes.

• Polyatomic ions: Charged groups of atoms (e.g., NO3-, SO42-).

Step-by-Step Guidance

1. Identify if the compound is ionic or covalent by checking the elements involved.

2. For ionic compounds, determine the cation (positive ion) and anion (negative ion). If the cation is a transition metal, use Roman numerals to indicate its charge.

3. For covalent compounds, use Greek prefixes to indicate the number of each atom present.

4. Apply the appropriate naming rules based on the compound type.

Try solving on your own before revealing the answer!

Q2. Electron Configuration Practice

Background

Topic: Electron Configuration

This section tests your understanding of how electrons fill atomic orbitals in both neutral atoms and ions, as well as recognizing ground and excited states.

Key Terms and Concepts:

• Electron configuration: The arrangement of electrons in an atom's orbitals.

• Ground state: Lowest energy arrangement of electrons.

• Excited state: At least one electron is in a higher energy orbital than in the ground state.

• Aufbau principle, Pauli exclusion principle, Hund's rule.

Step-by-Step Guidance

1. Determine the atomic number to find the number of electrons for the neutral atom.

2. Fill orbitals in order of increasing energy (1s, 2s, 2p, 3s, 3p, 4s, 3d, etc.).

3. For ions, add electrons for negative charges or remove electrons for positive charges.

4. For excited states, promote an electron from a lower to a higher energy orbital.

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Q3. Lewis Structures and Molecular Geometry

Background

Topic: Lewis Structures & VSEPR Theory

This section tests your ability to draw Lewis structures and predict molecular geometry using the VSEPR model.

Key Terms and Concepts:

• Lewis structure: Diagram showing valence electrons and bonds in a molecule.

• VSEPR model: Predicts 3D shape based on electron domains around the central atom.

• Electron domains: Bonds and lone pairs around the central atom.

Step-by-Step Guidance

1. Count the total number of valence electrons for all atoms in the molecule.

2. Draw single bonds between the central atom and surrounding atoms, then distribute remaining electrons as lone pairs to satisfy the octet rule.

3. Count the number of electron domains (bonds + lone pairs) around the central atom to determine geometry.

4. Use VSEPR theory to predict the 3D shape (e.g., tetrahedral, trigonal pyramidal).

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Q4. 3D Structure, Molecular Geometry, and Polarity

Background

Topic: Molecular Geometry & Polarity

This section tests your ability to identify molecular geometry and determine the polarity of bonds and molecules.

Key Terms and Concepts:

• Molecular geometry: The 3D arrangement of atoms in a molecule.

• Bond polarity: Determined by the difference in electronegativity ($\Delta EN$) between atoms.

• Molecular polarity: Depends on both bond polarity and molecular symmetry.

Step-by-Step Guidance

1. Identify the geometry of the molecule using VSEPR theory.

2. Calculate the electronegativity difference ($\Delta EN$) for each bond to determine if it is nonpolar covalent, polar covalent, or ionic.

3. Assess the overall symmetry of the molecule to determine if the molecule is polar or nonpolar.

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Q5. Lewis Structures, Molecular Geometry, and Polarity (CO2 and SO2)

Background

Topic: Lewis Structures, VSEPR, and Polarity

This section tests your ability to interpret Lewis structures, predict molecular geometry, and determine molecular polarity.

Key Terms and Concepts:

• Lewis structure: Shows bonding and lone pairs.

• Linear geometry: 180° bond angle, usually nonpolar if symmetrical.

• Bent geometry: Less than 180°, often polar due to asymmetry.

Step-by-Step Guidance

1. Examine the Lewis structure to count electron domains and determine geometry (linear or bent).

2. Calculate $\Delta EN$ for each bond to assess bond polarity.

3. Evaluate the symmetry of the molecule to determine if it is overall polar or nonpolar.

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Q6. Electronegativity Difference and Bond Type

Background

Topic: Electronegativity and Bond Classification

This section tests your ability to calculate the electronegativity difference ($\Delta EN$) and classify bonds as pure covalent, polar covalent, or ionic.

Key Terms and Concepts:

• Electronegativity: The tendency of an atom to attract electrons in a bond.

• $\Delta EN$: Difference in electronegativity between two atoms.

• Bond types: Pure covalent ($\Delta EN = 0$), polar covalent ($0 < \Delta EN < 2$), ionic ($\Delta EN > 2$).

Step-by-Step Guidance

1. Look up the electronegativity values for each element.

2. Subtract the smaller value from the larger to find $\Delta EN$.

3. Use the $\Delta EN$ value to classify the bond type.

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Q7. Molarity Calculation (Dilution)

Background

Topic: Solution Concentration and Dilution

This question tests your ability to use the dilution equation to calculate the volume of a concentrated solution needed to prepare a less concentrated solution.

Key Formula:

$M_1V_1 = M_2V_2$

• $M_1$ = initial (concentrated) molarity

• $V_1$ = volume of concentrated solution needed

• $M_2$ = final (diluted) molarity

• $V_2$ = final volume of diluted solution

Step-by-Step Guidance

1. Identify the known values: $M_1 = 0.672$ M, $M_2 = 0.208$ M, $V_2 = 485$ mL.

2. Write the dilution equation: $M_1V_1 = M_2V_2$.

3. Rearrange to solve for $V_1$: $V_1 = \frac{M_2V_2}{M_1}$.

4. Plug in the known values, but do not calculate the final answer yet.

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Q8. Molecular Weight Calculation

Background

Topic: Molar Mass Calculation

This question tests your ability to calculate the molecular weight (molar mass) of a compound by summing the atomic masses of all atoms in the formula.

Key Formula:

$\text{Molecular weight} = \sum (\text{number of atoms} \times \text{atomic mass})$

Step-by-Step Guidance

1. List the number of each type of atom in the formula (e.g., NaC2H3O2).

2. Multiply the number of each atom by its atomic mass.

3. Add the results to get the total molecular weight.

Try solving on your own before revealing the answer!