Q1. Convert the following formulas to names and names to formulas:

• MgSO4

• ZnCrO4

• (NH4)2CO3

• KClO4

• Ca3(PO4)2

• KMnO4

• Potassium chloride

• Tin (II) bromide

• Calcium oxide

• Barium chloride

• Aluminum hydride

Background

Topic: Ionic Compounds – Nomenclature and Formula Writing

This question tests your ability to name ionic compounds from their chemical formulas and to write correct formulas from their names, using rules for both simple and polyatomic ions.

Key Terms and Formulas

• Cation: Positively charged ion (usually a metal or ammonium).

• Anion: Negatively charged ion (nonmetal or polyatomic ion).

• Polyatomic ion: An ion composed of more than one atom (e.g., SO42-, NH4+).

• Stock system: Use Roman numerals to indicate the charge of transition metals (e.g., Tin (II)).

• Formula writing: Balance charges so the compound is neutral.

Step-by-Step Guidance

1. For each formula, identify the cation and anion. For example, in MgSO4, Mg is the cation and SO4 is the anion.

2. Recall the names of common polyatomic ions (e.g., SO42- is sulfate, CrO42- is chromate, CO32- is carbonate, etc.).

3. For formulas with transition metals or metals that can have multiple charges, check if a Roman numeral is needed in the name.

4. For names, write the symbol for each ion, determine their charges, and use subscripts to balance the charges so the overall compound is neutral.

5. For polyatomic ions, use parentheses if more than one is needed in the formula.

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Q2. What are the formulas of the compounds formed from the following ions?

• Na+ and NO3-

• K+ and SO42-

• Sr2+ and Cl-

Background

Topic: Writing Formulas for Ionic Compounds from Ions

This question tests your ability to write the correct chemical formula for an ionic compound given the ions involved, ensuring the overall charge is neutral.

Key Terms and Formulas

• Criss-cross method: Use the magnitude of each ion's charge as the subscript for the other ion.

• Neutral compound: The total positive and negative charges must balance.

Step-by-Step Guidance

1. Write the symbol and charge for each ion.

2. Determine the ratio of ions needed to balance the charges (the total positive charge must equal the total negative charge).

3. Apply the criss-cross method if needed: use the absolute value of each ion's charge as the subscript for the other ion.

4. Write the formula, omitting subscripts of 1.

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Q3. Fill in the missing subscript information to give formulas for the following compounds:

• Na?SO4

• Ba?(PO4)?

Background

Topic: Determining Subscripts in Ionic Compound Formulas

This question tests your ability to determine the correct subscripts in a chemical formula so that the compound is electrically neutral.

Key Terms and Formulas

• Subscript: Indicates the number of each ion in the formula.

• Charge balancing: The total positive and negative charges must add up to zero.

Step-by-Step Guidance

1. Write the charges for each ion: Na+, SO42-; Ba2+, PO43-.

2. Determine the lowest common multiple of the charges to find the correct ratio of ions.

3. Assign subscripts to each ion so that the total positive and negative charges are equal.

4. Write the completed formula, using parentheses for polyatomic ions if more than one is needed.

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Q4. What is WRONG with each of the following names of chemical compounds? For the elements involved, give the correct name.

• S and Mg: Sulfur magneside

• Ca and O: Calcium (II) oxide

• Sodium and nitrogen: Sodium nitrite

• Sn and Br: Tin bromide

• Strontium and sulfate: SrS

Background

Topic: Identifying and Correcting Errors in Ionic Compound Nomenclature

This question tests your understanding of the rules for naming ionic compounds, including the use of correct suffixes, Roman numerals, and polyatomic ion names.

Key Terms and Formulas

• Binary ionic compounds: Compounds with two elements, named as "cation + anion-ide".

• Polyatomic ions: Use the name of the polyatomic ion as is (e.g., sulfate, nitrite).

• Roman numerals: Only used for metals with variable charges (not for Group 1, 2, or Al, Zn, Ag).

Step-by-Step Guidance

1. For each name, identify the ions or elements involved and their correct charges.

2. Check if the name follows the correct convention for binary or polyatomic ionic compounds.

3. For transition metals, determine if a Roman numeral is needed and if the one given is correct.

4. For polyatomic ions, ensure the correct name is used (e.g., nitrite vs. nitride).

5. Write the correct name for each compound based on the ions involved.

Try solving on your own before revealing the answer!