Problem 67 - General Chemistry: Principles and Modern Applications

Question

Name the following compounds and specify which ones are best described as ionic: (a) \(\mathrm{OF}_{2} ;\) (b) \(\mathrm{XeF}_{2}\) (c) \(\operatorname{CuSO}_{3} ;\) (d) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\)

Step-by-Step Solution

Answer

The compounds are named as: (a) Oxygen difluoride, (b) Xenon difluoride, (c) Copper(II) Sulfate and (d) Diammonium hydrogen phosphate. Copper(II) Sulfate and Diammonium hydrogen phosphate are ionic compounds.

Step 1: Naming \( \mathrm{OF}_{2} \)

The compound \( \mathrm{OF}_{2} \) is a molecule formed from oxygen (O) and fluorine (F). Since it is formed from non-metals, we can suggest it's not an ionic compound. Oxygen difluoride is the correct IUPAC name for this compound.

Step 2: Naming \( \mathrm{XeF}_{2} \)

The compound \( \mathrm{XeF}_{2} \) is formed from Xenon (Xe) and Fluorine (F), both Non-Metals, thus it's probably not ionic. The naming of compounds of noble gases usually involve their full name and the non-metal they bond with. Hence, the name of \( \mathrm{XeF}_{2} \) is Xenon difluoride.

Step 3: Naming \( \operatorname{CuSO}_{3} \)

The compound \( \operatorname{CuSO}_{3} \) is formed by copper (Cu, a Metal) and Sulfate (SO3, an ion), thus likely an ionic compound. Copper has variable oxidation states, and in this case it is in the 2+ state, leading to the name: Copper(II) sulfate.

Step 4: Naming \( \left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4} \)

The compound \( \left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4} \) is formed by the ammonium ion (\( (NH_4)^+ \)) and the hydrogen phosphate ion (\( HPO_4^- \)). As it involves ions, it's an ionic compound. The IUPAC name would be: Diammonium hydrogen phosphate.

Key Concepts

Ionic Compounds

Ionic compounds are composed of charged particles known as ions. These ions are either positively charged cations or negatively charged anions. The nature of ionic compounds is a result of the electrostatic attraction between these oppositely charged ions. Typically, ionic compounds form when metals and non-metals react. Metals tend to lose electrons, forming positive ions, while non-metals gain electrons, forming negative ions. For example, in copper sulfate (CuSO extsubscript{3}), copper (Cu) is a metal and sulfate (SO extsubscript{3}) acts as a negative ion, making the compound ionic.

• Ionic compounds usually have high melting and boiling points.
• They conduct electricity when dissolved in water or melted, owing to the free movement of ions.
• They often form crystalline structures.

Understanding ionic compounds is crucial for naming them correctly using IUPAC nomenclature, especially since many metals exhibit multiple oxidation states. This naming requires specifying the cation's oxidation state within the compound.

Non-Metal Compounds

Non-metal compounds consist entirely of non-metal elements. These compounds are often formed by covalent bonds, in which atoms share electrons rather than transferring them entirely as in ionic compounds. For example, compounds like oxygen difluoride (OF extsubscript{2}) and xenon difluoride (XeF extsubscript{2}) demonstrate primary non-metal bonding, where both oxygen and xenon are non-metals.

• Non-metal compounds typically have lower melting and boiling points compared to ionic compounds.
• They do not conduct electricity because they lack free ions.
• Their physical state can range from gases to solids at room temperature.

Naming non-metal compounds often involves using prefixes such as "mono-", "di-", "tri-" to indicate the number of each type of atom present in the compound, following a systematic convention.

Oxidation States

Oxidation states, also known as oxidation numbers, are hypothetical charges assigned to atoms in molecules or complexes based on the assumption of complete electron transfer. These states help determine the electron configuration and name of a compound. In ionic compounds, especially those with transition metals like copper, different oxidation states must be considered.
For example, copper can exhibit more than one oxidation state, such as +1 or +2. For CuSO extsubscript{3}, copper is in the +2 oxidation state, hence the name copper(II) sulfate. The Roman numeral II indicates the specific oxidation state of copper in this compound.

• Oxidation states are crucial for understanding redox reactions.
• They help in balancing chemical equations.
• When naming compounds, correct identification of oxidation states is essential for clear communication.

Mastery of oxidation states facilitates a deeper comprehension of the chemical reactivity and properties of substances.