Question

Assign oxidation states to all of the atoms in each of the following: a. \(\mathrm{Na}_{3} \mathrm{PO}_{4}\) b. \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) c. \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) d. \(\mathrm{Na}_{3} \mathrm{P}\)

Short answer

The oxidation states for the given compounds are: a. \(\mathrm{Na}_{3} \mathrm{PO}_{4}\): Na = +1, P = +5, and O = -2. b. \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\): Na = +1, H = +1, P = +6, and O = -2. c. \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\): Na = +1, H = +1, P = +5, and O = -2. d. \(\mathrm{Na}_{3} \mathrm{P}\): Na = +1 and P = -3.

Step-by-step solution

Identify the atoms and their common oxidation states

In this compound, we have sodium (Na), phosphorus (P), and oxygen (O). Sodium, as an alkali metal, has a common oxidation state of +1. Oxygen typically has an oxidation state of -2, while phosphorus usually is between +3 and +5.

Apply the rules for assigning oxidation states

There are three sodium atoms with an oxidation state of +1 each, giving a total of +3. We have four oxygen atoms with a -2 oxidation state each, which gives a total of -8. Since the net charge of the compound is zero, the oxidation state of the phosphorus (P) must be +5 (such that +3 + (-8) + x = 0, where x is the oxidation state of P).

Assign the oxidation states

The oxidation states for \(\mathrm{Na}_{3} \mathrm{PO}_{4}\) are: Na = +1, P = +5, and O = -2. b. \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\)

Identify the atoms and their common oxidation states

We have sodium (Na), hydrogen (H), phosphorus (P), and oxygen (O) in this compound. Sodium has a common oxidation state of +1, hydrogen typically has a +1 oxidation state, oxygen has a -2 oxidation state, and phosphorus can have oxidation states between +3 and +5.

Apply the rules for assigning oxidation states

There is one sodium atom with an oxidation state of +1 and two hydrogen atoms with an oxidation state of +1 each, giving a total of +2. We have four oxygen atoms with a -2 oxidation state each, which gives a total of -8. Since the net charge of the compound is zero, the oxidation state of the phosphorus (P) must be +6 (such that +2 + (-8) + x = 0, where x is the oxidation state of P).

Assign the oxidation states

The oxidation states for \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) are: Na = +1, H = +1, P = +6, and O = -2. c. \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\)

Identify the atoms and their common oxidation states

We have sodium (Na), hydrogen (H), phosphorus (P), and oxygen (O) in this compound. Sodium has a common oxidation state of +1, hydrogen typically has a +1 oxidation state, oxygen has a -2 oxidation state, and phosphorus can have oxidation states between +3 and +5.

Apply the rules for assigning oxidation states

There are two sodium atoms with an oxidation state of +1 each, giving a total of +2. We have one hydrogen atom with an oxidation state of +1, and four oxygen atoms with a -2 oxidation state each, giving a total of -8. Since the net charge of the compound is zero, the oxidation state of the phosphorus (P) must be +5 (such that +2 + (+1) + (-8) + x = 0, where x is the oxidation state of P).

Assign the oxidation states

The oxidation states for \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) are: Na = +1, H = +1, P = +5, and O = -2. d. \(\mathrm{Na}_{3} \mathrm{P}\)

Identify the atoms and their common oxidation states

In this compound, we have sodium (Na) and phosphorus (P). Sodium has a common oxidation state of +1, and phosphorus can have oxidation states between -3 and +5.

Apply the rules for assigning oxidation states

There are three sodium atoms with an oxidation state of +1 each, giving a total of +3. Since the net charge of the compound is zero, the oxidation state of the phosphorus (P) must be -3 (such that +3 + x = 0, where x is the oxidation state of P).

Assign the oxidation states

The oxidation states for \(\mathrm{Na}_{3} \mathrm{P}\) are: Na = +1 and P = -3.

Key concepts

Understanding Chemical Compounds

Chemical compounds are substances consisting of two or more different elements bonded together. These compounds can have various types of bonds, such as ionic, covalent, or metallic. Each element within a compound has its unique properties, but when they combine, they create new properties for the compound.
For instance, a well-known compound is sodium chloride (table salt). This compound is formed from sodium, a highly reactive metal, and chlorine, a toxic gas. However, when combined, they form a stable and safe substance used in everyday cooking.

• Compounds are very different from their constituent elements.
• The properties of a compound are distinct and unique.
• Compounds can interact with each other in various chemical reactions.

Overall, understanding chemical compounds is crucial as they are the building blocks of matter and exist in various forms around us, such as water, air, and food.

Exploring Sodium Phosphate

Sodium phosphate is a common chemical compound made up of sodium (Na), phosphorus (P), and oxygen (O). Its chemical formula can vary depending on the type, but one common form is trisodium phosphate (\(\mathrm{Na}_{3}\mathrm{PO}_{4}\)). It is often used in various applications, including as a food additive, cleaning agent, and in water treatment.
Sodium phosphate can exist in multiple forms, such as monobasic (\(\mathrm{NaH}_{2}\mathrm{PO}_{4}\)), dibasic (\(\mathrm{Na}_{2}\mathrm{HPO}_{4}\)), and tribasic (\(\mathrm{Na}_{3}\mathrm{PO}_{4}\)). Each type contains varying ratios of sodium to phosphorus and differs in their chemical behavior and applications.

• Trisodium phosphate is often used for cleaning due to its high alkalinity.
• Monosodium phosphate is used to control pH levels in food.
• Disodium phosphate is employed in foods to prevent coagulation.

The versatility of sodium phosphate makes it a vital part of many industrial and food processes, demonstrating its importance in everyday life.

Basics of Redox Reactions

Redox reactions, short for reduction-oxidation reactions, are essential processes in chemistry involving the transfer of electrons between two species. In these reactions:

• Reduction is the gain of electrons, leading to a decrease in oxidation state.
• Oxidation is the loss of electrons, resulting in an increase in oxidation state.

A simple way to remember this is through the mnemonic "LEO the lion says GER" - Loss of Electrons is Oxidation, Gain of Electrons is Reduction.
Redox reactions are crucial in various biological and chemical processes, such as cellular respiration, combustion, and corrosion. These reactions can also be found in electrochemical cells, where chemical energy is converted into electrical energy, or vice versa.

• Redox reactions often involve the movement of oxygen molecules in addition to electrons.
• Balancing such reactions requires ensuring both mass and charge are conserved.
• An oxidizing agent gains electrons and is reduced.
• A reducing agent loses electrons and is oxidized.

Understanding redox reactions is vital for grasping how many natural and technological processes operate.

Introduction to Ionic Compounds

Ionic compounds are formed by the complete transfer of electrons from one atom to another, resulting in the formation of positive and negative ions. These ions are bonded together by strong electrostatic forces, creating a rigid and stable structure.

• Cations, which are positively charged ions, generally form from metal atoms.
• Anions, negatively charged ions, typically originate from non-metals.

A classic example of an ionic compound is sodium chloride (NaCl), where sodium donates an electron to chlorine, forming Na⁺ and Cl⁻ ions.
Ionic compounds have distinct properties:

• They usually have high melting and boiling points owing to strong ionic bonds.
• They tend to dissolve well in water, allowing them to conduct electricity when in solution.
• The crystal lattice structure gives them a solid, brittle form at room temperature.

These compounds are abundant in nature and used widely in industries, making them fundamental to chemical science.