Question

Identify the five compounds of \(\mathrm{H}, \mathrm{N},\) and \(\mathrm{O}\) described as follows. For each compound, write a Lewis structure that is consistent with the information given. a. All the compounds are electrolytes, although not all of them are strong electrolytes. Compounds \(\mathrm{C}\) and \(\mathrm{D}\) are ionic and compound \(\mathrm{B}\) is covalent. b. Nitrogen occurs in its highest possible oxidation state in compounds \(\mathrm{A}\) and \(\mathrm{C}\); nitrogen occurs in its lowest possible oxidation state in compounds \(\mathrm{C}, \mathrm{D}\), and \(\mathrm{E}\). The formal charge on both nitrogens in compound \(\mathrm{C}\) is \(+1\); the formal charge on the only nitrogen in compound \(\mathrm{B}\) is 0. c. Compounds \(\mathrm{A}\) and \(\mathrm{E}\) exist in solution. Both solutions give off gases. Commercially available concentrated solutions of compound A are normally 16\(M .\) The commercial, concentrated solution of compound \(E\) is 15\(M .\) d. Commercial solutions of compound E are labeled with a misnomer that implies that a binary, gaseous compound of nitrogen and hydrogen has reacted with water to produce ammonium ions and hydroxide ions. Actually, this reaction occurs to only a slight extent. e. Compound \(D\) is 43.7\(\% \mathrm{N}\) and 50.0\(\%\) O by mass. If compound D were a gas at STP, it would have a density of 2.86 \(\mathrm{g} / \mathrm{L} .\) f. A formula unit of compound \(\mathrm{C}\) has one more oxygen than a formula unit of compound \(\mathrm{D}\). Compounds \(\mathrm{C}\) and \(\mathrm{A}\) have one ion in common when compound \(\mathrm{A}\) is acting as a strong electrolyte. g. Solutions of compound \(\mathrm{C}\) are weakly acidic; solutions of compound \(\mathrm{A}\) are strongly acidic; solutions of compounds \(\mathrm{B}\) and \(\mathrm{E}\) are basic. The titration of 0.726 g compound \(\mathrm{B}\) requires 21.98 \(\mathrm{mL}\) of 1.000 \(\mathrm{M} \mathrm{HCl}\) for complete neutralization.

Short answer

In conclusion, the five compounds are as follows: - Compound A: Nitric Acid (HNO₃) - Compound B: Ammonia (NH₃) - Compound C: Ammonium Nitrate (NH₄NO₃) - Compound D: Nitrogen Dioxide (NO₂) - Compound E: Ammonium Hydroxide (NH₄OH)

Step-by-step solution

Compound A

From the information given: - Compound A is a strong electrolyte - Nitrogen is in its highest oxidation state - The solution gives off gases - It is strongly acidic Considering the information, compound A can be identified as Nitric Acid (HNO₃). It is a strong acid and a strong electrolyte. The oxidation state of nitrogen in HNO₃ is +5, which is its highest possible oxidation state.

Compound B

From the information given: - Compound B is covalent - Nitrogen is in its lowest oxidation state - The formal charge on the nitrogen atom is 0 - It is basic Considering the information, compound B can be identified as Ammonia (NH₃). It is a covalent compound that acts as a base in solution. The oxidation state of nitrogen in NH₃ is -3, which is its lowest possible oxidation state. The formal charge on the nitrogen atom is 0.

Compound C

From the information given: - Compound C is ionic - Nitrogen is in its highest and lowest oxidation states - Formal charge on both nitrogens is +1 - Has one more oxygen atom than compound D Considering the information, compound C can be identified as Ammonium Nitrate (NH₄NO₃). It is an ionic compound with nitrogen in both its highest and lowest oxidation states. The formal charge on each nitrogen atom in the ammonium (NH₄+) ion is +1, and the formal charge on nitrogen in the nitrate (NO₃-) ion is 0. It has one more oxygen atom than compound D (which we will determine later).

Compound D

From the information given: - 43.7% N and 50.0% O by mass - Has one less oxygen atom than compound C (NH₄NO₃) Based on the mass percentages, we can determine the empirical formula of compound D as NO₂. This means that compound D is Nitrogen Dioxide. It has one less oxygen atom than compound C (NH₄NO₃).

Compound E

From the information given: - Solutions give off gases - Labeled with a misnomer implying NH₃ reacting with water Considering the information, compound E can be identified as Ammonium Hydroxide (NH₄OH). The misnomer refers to the incorrect naming as if it were a direct result of ammonia (NH₃) reacting with water, which occurs only to a slight extent in reality. In conclusion, the five compounds are as follows: - Compound A: Nitric Acid (HNO₃) - Compound B: Ammonia (NH₃) - Compound C: Ammonium Nitrate (NH₄NO₃) - Compound D: Nitrogen Dioxide (NO₂) - Compound E: Ammonium Hydroxide (NH₄OH)

Key concepts

Lewis Structures

Lewis structures are a way to represent molecules showing all the atoms, bonds, and unshared electron pairs. Each molecule has its own distinct Lewis structure that helps visualize how electrons are shared or transferred between atoms. To draw a Lewis structure, start by counting all the valence electrons available from each atom. Then, arrange atoms to form a skeleton structure, connecting them using single bonds initially. Complement the structure by adding electrons to fulfill the octet rule for each atom, which generally means having a complete set of 8 valence electrons.
- Nitric Acid
For example, in Nitric Acid, compound A (HNO₃), you represent nitrogen (N) bonded to a hydroxyl group (-OH) and two oxygen atoms, one with a double bond and the other with a single bond and a negative charge. Nitrogen exhibits a +5 oxidation state.
- Ammonia
In contrast, Ammonia (NH₃), compound B, involves a single nitrogen atom bonded to three hydrogen atoms, satisfying the nitrogen with a full octet using lone pair electrons. Understanding Lewis structures is essential for balancing chemical equations, predicting molecular shapes, and determining possible reactions based on electron arrangements.

Electrolytes

Electrolytes are substances that dissociate into ions when dissolved in water, conducting electricity. They are broadly classified into strong and weak electrolytes, based on their ionized percentage in solution.
- Strong Electrolytes
Strong electrolytes, like HNO₃ (compound A), completely dissociate in solution, providing a high concentration of ions, thus showing strong electrical conductivity. These include most salts, strong acids, and bases.
- Weak Electrolytes
Weak electrolytes, such as NH₄OH (compound E), only partially dissociate, resulting in lower ionic concentration and hence, weaker conductivity. The distinction between strong and weak electrolytes is crucial in predicting the behavior of solutions and their reaction to electricity. For students, comprehending these differences helps you understand phenomena like electrolyte balance in biological systems and industrial applications.

Oxidation States

The oxidation state or number represents the number of electrons an atom gains, loses, or shares when it forms chemical bonds. It helps in determining electron flow in redox reactions and understanding molecule reactivity.
- Nitrogen's Variable Oxidation States
In the exercise, nitrogen exhibits both its highest (+5) and lowest (-3) oxidation states. In nitric acid (HNO₃), nitrogen is at its highest due to the strong pull from oxygen. Conversely, in ammonia (NH₃), nitrogen is at its lowest oxidation state due to the electron-donating hydrogen atoms. Calculating oxidation states is vital in redox reactions and determining molecule stability. Identifying oxidation state changes allows you to balance equations and predict possible reactions effectively.

Acids and Bases

Acids and bases are two fundamental concepts in chemistry, characterized mainly by their ability to donate or accept protons (H⁺ ions) respectively. The ionizable protons (H⁺) are key to many chemical reactions affecting both organic and inorganic chemistry.
- Acids
For instance, Nitric Acid (HNO₃), referred to in the exercise, acts as a strong acid. Its full dissociation in water means it readily donates protons, contributing to its acidic nature.
- Bases
On the other hand, Ammonia (NH₃) acts as a base, meaning it tends to accept protons. Compound E, Ammonium Hydroxide (NH₄OH), is another example where it behaves like a weak base due to partial ionization in water. Understanding acids and bases leads to insights about pH balance, reaction predictability, and titration processes. This knowledge is vital for further study in chemistry, involving reaction mechanisms and solution chemistry adjustments.