Chemical Formula Writing Worksheet - Answers

The image provided is a "Chemical Formula Writing Worksheet - Answers" that lists various chemical compounds and their corresponding formulas, charges, and other properties. Below is an explanation of how to interpret and use this worksheet effectively:

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Key Components of the Worksheet

1. Columns in the Table:
- Name: The name of the compound.
- Formula: The chemical formula of the compound.
- Molar Mass (g/mol): The molar mass of the compound, calculated by summing the atomic masses of all atoms in the formula.
- % Composition (%): The percentage by mass of each element in the compound.
- Valence Electrons: The number of valence electrons for the ions involved in the compound.
- Charge: The charge on the ion(s) in the compound.
- Type of Bond: Indicates whether the bond is ionic or covalent.

2. Rows in the Table:
Each row corresponds to a specific compound, providing detailed information about its composition and properties.

3. Example Compound Analysis:
Let’s take one example from the table:
- Compound: Sodium Chloride (NaCl)
- Formula: NaCl
- Molar Mass: 58.44 g/mol
- % Composition:
- Sodium (Na): ~39.34%
- Chlorine (Cl): ~60.66%
- Valence Electrons:
- Sodium (Na⁺): 1 electron lost
- Chlorine (Cl⁻): 1 electron gained
- Charge:
- Sodium (Na⁺): +1
- Chlorine (Cl⁻): -1
- Type of Bond: Ionic

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How to Use This Worksheet

1. Understanding Chemical Formulas:
- The worksheet provides the correct chemical formulas for various compounds. For example, sodium chloride is written as \( \text{NaCl} \), not \( \text{Na}_2\text{Cl}_2 \). This helps in learning how to balance charges between cations and anions.

2. Calculating Molar Mass:
- The molar mass is calculated by adding the atomic masses of all atoms in the formula. For example:
- Sodium (Na): 22.99 g/mol
- Chlorine (Cl): 35.45 g/mol
- Total: \( 22.99 + 35.45 = 58.44 \) g/mol

3. Determining % Composition:
- The percentage composition shows the relative mass contribution of each element in the compound. For example, in NaCl:
- % Na = \( \frac{22.99}{58.44} \times 100 = 39.34\% \)
- % Cl = \( \frac{35.45}{58.44} \times 100 = 60.66\% \)

4. Valence Electrons and Charges:
- Valence electrons help determine the charge on ions. For example:
- Sodium (Na) loses 1 electron to become \( \text{Na}^+ \).
- Chlorine (Cl) gains 1 electron to become \( \text{Cl}^- \).

5. Identifying Bond Types:
- The type of bond (ionic or covalent) is indicated. Ionic bonds occur between metals and nonmetals, while covalent bonds occur between nonmetals.

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General Steps to Solve Similar Problems

1. Identify the Elements:
Determine the elements involved in the compound.

2. Write the Formula:
Use the periodic table to write the correct chemical formula by balancing the charges of the ions.

3. Calculate Molar Mass:
Sum the atomic masses of all atoms in the formula.

4. Determine % Composition:
Calculate the percentage contribution of each element using the formula:
\[
\text{% Composition} = \left( \frac{\text{Mass of Element}}{\text{Molar Mass of Compound}} \right) \times 100
\]

5. Analyze Valence Electrons and Charges:
Identify the number of valence electrons and the resulting charges on ions.

6. Classify the Bond Type:
Determine whether the bond is ionic (metal + nonmetal) or covalent (nonmetal + nonmetal).

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Example Problem Solution

#### Problem:
Write the chemical formula, calculate the molar mass, and determine the % composition for magnesium oxide (MgO).

#### Solution:
1. Formula:
- Magnesium (Mg) forms \( \text{Mg}^{2+} \) (loses 2 electrons).
- Oxygen (O) forms \( \text{O}^{2-} \) (gains 2 electrons).
- To balance charges: \( \text{MgO} \).

2. Molar Mass:
- Magnesium (Mg): 24.31 g/mol
- Oxygen (O): 16.00 g/mol
- Total: \( 24.31 + 16.00 = 40.31 \) g/mol

3. % Composition:
- % Mg = \( \frac{24.31}{40.31} \times 100 = 60.31\% \)
- % O = \( \frac{16.00}{40.31} \times 100 = 39.69\% \)

4. Valence Electrons and Charges:
- Magnesium (Mg): 2 valence electrons lost → \( \text{Mg}^{2+} \)
- Oxygen (O): 6 valence electrons gained → \( \text{O}^{2-} \)

5. Bond Type:
- Ionic bond (metal + nonmetal).

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Final Answer

\[
\boxed{\text{MgO, 40.31 g/mol, Mg: 60.31%, O: 39.69%, Ionic}}
\]

This worksheet is a valuable tool for practicing and mastering the skills needed to write chemical formulas, calculate molar masses, and analyze the composition and bonding of compounds.