Problem 115 - Chemistry Matter and Change

Question

Observe and Infer Identify the mistakes in the incorrect formulas and formula names, and design a flowchart to prevent the mistakes. a. copper acetate b. \(\mathrm{Mg}_{2} \mathrm{O}_{2}\) c. \(\mathrm{Pb}_{2} \mathrm{O}_{5}\) d. disodium oxide e. \(\mathrm{Al}_{2} \mathrm{SO}_{43}\)

Step-by-Step Solution

Answer

The corrected formulas and names are: a. Copper acetate: \(\mathrm{Cu(CH_3COO)_2}\) b. Magnesium oxide: \(\mathrm{MgO}\) c. Lead (IV) oxide: \(\mathrm{PbO_2}\) d. Disodium oxide: \(\mathrm{Na_2O}\) e. Aluminum sulfate: \(\mathrm{Al_2(SO_4)_3}\) To prevent mistakes, follow this flowchart: 1. Start with the given formula/compound name 2. Check prefixes, typos, and element names 3. Verify stoichiometry, charges, and subscripts 4. Make necessary corrections 5. Confirm the correct formula and name 6. End

Step 1: Correcting copper acetate

The correct formula for copper acetate is \(\mathrm{Cu(CH_3COO)_2}\). The name was broadly correct, but the formula was missing.

Step 2: Correcting \(\mathrm{Mg}_{2} \mathrm{O}_{2}\)

The correct formula for the magnesium oxide is \(\mathrm{MgO}\). The given formula has incorrect subscripts which need to be simplified.

Step 3: Correcting \(\mathrm{Pb}_{2} \mathrm{O}_{5}\)

The correct formula for lead (IV) oxide is \(\mathrm{PbO_2}\). The given formula has incorrect subscripts and must be simplified.

Step 4: Correcting disodium oxide

The correct formula for disodium oxide is \(\mathrm{Na_2O}\). The name was broadly correct, but the formula was missing.

Step 5: Correcting \(\mathrm{Al}_{2} \mathrm{SO}_{43}\)

The correct formula for aluminum sulfate is \(\mathrm{Al_2(SO_4)_3}\). The given formula had incorrect subscripts which needed to be corrected, as well as a formatting error with the parentheses.

Step 6: Designing a flowchart to prevent mistakes

1. Start with the formula/compound name given 2. Check if the name contains correct prefixes for elements (di-, tri-, etc.) 3. Check for typos in the formula or names of elements 4. Check if the compound is formed with correct stoichiometry (presence of correct number of atoms in the formula) 5. Check if the charges of ions present in the formula are balanced 6. Check if simplified subscripts have been used for the compound 7. Make necessary changes and corrections 8. Confirm the correct formula and name 9. End

Key Concepts

Stoichiometry

Stoichiometry is the division of chemistry that deals with the relative quantities of reactants and products in chemical reactions. It is a foundational concept for understanding how to balance equations and predict the amounts of substances involved in reactions. For instance, the stoichiometry of a compound dictates the exact ratio of atoms of each element in that compound.

When correcting a chemical formula such as \( \mathrm{Mg}_2\mathrm{O}_2 \), understanding stoichiometry becomes essential. Magnesium and oxygen react in a 1:1 ratio to form magnesium oxide, which means for every magnesium atom, there should be only one oxygen atom, resulting in the corrected formula \( \mathrm{MgO} \). This reflects the stoichiometry of the compound, showing a simplified and accurate representation of the ratio of magnesium to oxygen atoms.

Compound Naming Conventions

The naming of chemical compounds follows specific conventions to ensure clarity and consistency. For example, the name 'disodium oxide' implies a compound made from sodium and oxygen. By convention, metal elements such as sodium are mentioned first, followed by the nonmetal with an 'ide' suffix, in this case, 'oxide' for oxygen. This helps in understanding the composition of the compound.

When correcting a name or a formula, we must ensure that we follow these IUPAC (International Union of Pure and Applied Chemistry) conventions. The compound name 'disodium oxide' correlates to the formula \( \mathrm{Na_2O} \), with 'di-' indicating that two sodium atoms are bonded to one oxygen atom. This systemic naming helps students to infer the chemical formula from the compound name and vice versa.

Chemical Formula Correction

Correcting chemical formulas is crucial to accurately represent the composition of substances. Errors in formulas can lead to misunderstandings about the nature of the compound. For example, the incorrectly given formula \( \mathrm{Al}_2\mathrm{SO}_{43} \) does not accurately represent aluminum sulfate, a commonly used compound. The correct formula is \( \mathrm{Al}_2(\mathrm{SO}_4)_3 \), indicating that two aluminum ions combine with three sulfate \( \mathrm{SO}_4^{2-} \) ions.

When correcting formulas, it's important to pay attention to subscript numbers, which denote the number of atoms of each element, and to correctly use parentheses to denote the grouping in polyatomic ions, as in aluminum sulfate.

Ion Charge Balancing

Ion charge balancing is a key aspect of creating correct chemical formulas. Since compounds must be electrically neutral, the total positive charge must balance the total negative charge. For a compound like copper acetate, remembering that copper typically has a \( +2 \) charge and acetate \( \mathrm{CH_3COO^-} \) has a \( -1 \) charge will guide you to the correct formula, \( \mathrm{Cu(CH_3COO)_2} \). The subscript '2' after the acetate ion indicates that two acetate ions, each with a \( -1 \) charge, are required to counterbalance the \( +2 \) charge of the copper ion, making the entire compound neutral.

This process requires a solid understanding of common ions and their charges. By balancing these charges, one can determine the correct subscripts for the ions in the formula, ensuring the compound is accurately represented.