Question

Write the chemical formula for each of the following compounds, and indicate the oxidation state of nitrogen in each: (a) nitric oxide, (b) hydrazine, (c) potassium cyanide, (d) sodium nitrite, (e) ammonium chloride, (f) lithium nitride.

Short answer

(a) Nitric oxide: \(NO\), oxidation state of nitrogen is +2. (b) Hydrazine: \(N_2H_4\), oxidation state of nitrogen is -2. (c) Potassium cyanide: \(KCN\), oxidation state of nitrogen is -3. (d) Sodium nitrite: \(NaNO_2\), oxidation state of nitrogen is +3. (e) Ammonium chloride: \(NH_4Cl\), oxidation state of nitrogen is -3. (f) Lithium nitride: \(Li_3N\), oxidation state of nitrogen is -3.

Step-by-step solution

a) Nitric Oxide

Nitric oxide (NO) consists of one nitrogen (N) atom and one oxygen (O) atom. Nitrogen has +2 oxidation state and oxygen has -2 oxidation state. Thus, the chemical formula for nitric oxide is: \[ NO \] The oxidation state of nitrogen in this compound is +2.

b) Hydrazine

Hydrazine (N2H4) is formed by two nitrogen (N) atoms and four hydrogen (H) atoms. In this compound, nitrogen has -2 oxidation state and hydrogen has +1 oxidation state. So, the chemical formula for hydrazine is: \[ N_2H_4 \] The oxidation state of nitrogen in this compound is -2.

c) Potassium Cyanide

Potassium cyanide (KCN) is formed by one potassium (K) atom, one carbon (C) atom, and one nitrogen (N) atom. In this compound, potassium has +1 oxidation state, carbon has +2 oxidation state, and nitrogen has -3 oxidation state. The chemical formula for potassium cyanide is: \[ KCN \] The oxidation state of nitrogen in this compound is -3.

d) Sodium Nitrite

Sodium nitrite (NaNO2) consists of one sodium (Na) atom, one nitrogen (N) atom, and two oxygen (O) atoms. In this compound, sodium has +1 oxidation state, nitrogen has +3 oxidation state, and oxygen has -2 oxidation state. The chemical formula for sodium nitrite is: \[ NaNO_2 \] The oxidation state of nitrogen in this compound is +3.

e) Ammonium Chloride

Ammonium chloride (NH4Cl) consists of one nitrogen (N) atom, four hydrogen (H) atoms, and one chlorine (Cl) atom. In this compound, nitrogen has -3 oxidation state, hydrogen has +1 oxidation state, and chlorine has -1 oxidation state. The chemical formula for ammonium chloride is: \[ NH_4Cl \] The oxidation state of nitrogen in this compound is -3.

f) Lithium Nitride

Lithium nitride (Li3N) consists of three lithium (Li) atoms and one nitrogen (N) atom. In this compound, lithium has +1 oxidation state, and nitrogen has -3 oxidation state. The chemical formula for lithium nitride is: \[ Li_3N \] The oxidation state of nitrogen in this compound is -3.

Key concepts

Chemical Formulas

Understanding chemical formulas is foundational in the study of chemistry, as they represent the types and numbers of atoms present in a compound.
For example, when we look at nitric oxide, the chemical formula is denoted as NO, which specifies that it consists of one nitrogen (N) atom and one oxygen (O) atom.

The subscripts in chemical formulas indicate the quantity of each atom; for instance, in hydrazine (N₂H₄), the '2' tells us that there are two atoms of nitrogen, and the '4' shows there are four atoms of hydrogen. Potassium cyanide (KCN) and sodium nitrite (NaNO₂) are other examples emphasizing the diversity of these molecular structures.

It is essential to learn how to read these symbols correctly to understand the composition of compounds and to predict how they might behave in different chemical reactions.

Oxidation-Reduction Chemistry

The concept of oxidation states in chemistry is crucial for identifying how electrons are distributed among atoms in a compound.
Oxidation states can indicate whether a substance is likely to gain or lose electrons in chemical reactions, which are called oxidation-reduction (redox) reactions.

For example, in nitric oxide, nitrogen has an oxidation state of +2. This suggests it has lost two electrons when compared 'to its elemental state. Conversely, in hydrazine, the nitrogen appears with an oxidation state of -2, implying it has gained electrons.

Understanding these states helps predict the behavior of substances during redox reactions. The movement of electrons from one molecule to another is fundamental to such chemical processes, affecting the energy transfer that underpins a vast range of applications, from biological processes to industrial manufacturing.

Naming Chemical Compounds

The ability to name chemical compounds correctly is a key skill in chemistry, allowing clear communication among scientists. Each name provides information about the structure and components of a compound.
For example, 'ammonium chloride' describes a compound made up of ammonium (NH₄⁺) ions and chloride (Cl⁻) ions, resulting in NH₄Cl.

The names can also reflect the systematic nomenclature where 'lithium nitride' tells us that the compound contains lithium (Li) and the nitride ion (N³⁻), resulting in Li₃N.

This systematic approach uses specific rules, such as using suffixes like -ide, -ite, or -ate, to provide additional details regarding the oxidation states and composition of the compound. Learning to name chemical compounds properly ensures that you can both identify and describe the nuances of a chemical's makeup.