Problem 119 - Chemistry: An Atoms-Focused Approach

Question

Many nonmetal oxides react with water to form acidic solutions. Give the formulas of the acids produced in the following reactions: a. \(P_{4} O_{10}+6 H_{2} O \rightarrow ?\) b. \(\mathrm{SeO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow ?\) c. \(\mathrm{B}_{2} \mathrm{O}_{3}+3 \mathrm{H}_{2} \mathrm{O} \rightarrow ?\)

Step-by-Step Solution

Answer

Answer: The acids produced in the reactions are H3PO4 (orthophosphoric acid), H2SeO3 (selenous acid), and H3BO3 (boric acid).

Step 1: Determine the oxidation state of phosphorus and oxygen in P4O10

In P4O10, the oxidation states of phosphorus (P) and oxygen (O) are +5 and -2, respectively.

Step 2: Identify the reaction type and possible products

The given reaction is between a nonmetal oxide (P4O10) and water, so we are looking for an acid product. The oxidation state of P will remain the same in the acid product, while H will come from the water molecules.

Step 3: Write the correct acid formula and balance the equation

Considering the oxidation state of P (+5) and the fact that an acidic solution is formed, the acid produced must be H3PO4 (orthophosphoric acid). The balanced equation is: \(P_{4}O_{10} + 6H_{2}O \rightarrow 4H_{3}PO_{4}\) #b) Reaction between SeO2 and H2O#

Step 1: Determine the oxidation state of selenium and oxygen in SeO2

In SeO2, the oxidation states of selenium (Se) and oxygen (O) are +4 and -2, respectively.

Step 2: Identify the reaction type and possible products

The given reaction is between a nonmetal oxide (SeO2) and water, so we are looking for an acid product. The oxidation state of Se will remain the same in the acid product, while H will come from the water molecules.

Step 3: Write the correct acid formula and balance the equation

Considering the oxidation state of Se (+4) and the fact that an acidic solution is formed, the acid produced must be H2SeO3 (selenous acid). The balanced equation is: \(SeO_{2} + H_{2}O \rightarrow H_{2}SeO_{3}\) #c) Reaction between B2O3 and H2O#

Step 1: Determine the oxidation state of boron and oxygen in B2O3

In B2O3, the oxidation states of boron (B) and oxygen (O) are +3 and -2, respectively.

Step 2: Identify the reaction type and possible products

The given reaction is between a nonmetal oxide (B2O3) and water, so we are looking for an acid product. The oxidation state of B will remain the same in the acid product, while H will come from the water molecules.

Step 3: Write the correct acid formula and balance the equation

Considering the oxidation state of B (+3) and the fact that an acidic solution is formed, the acid produced must be H3BO3 (boric acid). The balanced equation is: \(B_{2}O_{3} + 3H_{2}O \rightarrow 2H_{3}BO_{3}\)

Key Concepts

nonmetal oxides

Nonmetal oxides are compounds composed of oxygen atoms bonded to nonmetal elements. These oxides are significant in chemistry because they react with water to form acidic solutions. They often serve as the "acid anhydrides" that give rise to corresponding acids upon hydration.
Nonmetal oxides include substances like phosphorus pentoxide \(\text{P}_{4}\text{O}_{10}\), selenium dioxide \(\text{SeO}_{2}\), and boron trioxide \(\text{B}_{2}\text{O}_{3}\).
Upon interacting with water, these substances can produce various types of acids:

• Phosphorus pentoxide reacts with water to create orthophosphoric acid \(\text{H}_{3}\text{PO}_{4}\).
• Selenium dioxide forms selenous acid \(\text{H}_{2}\text{SeO}_{3}\).
• Boron trioxide results in boric acid \(\text{H}_{3}\text{BO}_{3}\).

This process involves the transfer and reconfiguration of atoms to maintain the basic characteristics and oxidation states of the reacting nonmetal. Understanding these reactions allows chemists to predict the type of acid that will be produced when a nonmetal oxide meets water.

oxidation states

Oxidation states, also known as oxidation numbers, are a way of tracking how electrons are transferred in chemical reactions. An atom's oxidation state is its hypothetical charge if all bonds to it were completely ionic. For nonmetal oxides, understanding oxidation states is key in determining the resulting acid when reacting with water.
Each nonmetal in a compound has a specific oxidation state:

• In phosphorus pentoxide \(\text{P}_{4}\text{O}_{10}\), phosphorus has an oxidation state of +5.
• In selenium dioxide \(\text{SeO}_{2}\), selenium is at +4.
• In boron trioxide \(\text{B}_{2}\text{O}_{3}\), boron has an oxidation state of +3.

When these oxides interact with water, the nonmetals retain their oxidation states in the resultant acids. This retention helps in predicting the acid's structure and the number of hydrogen atoms involved. For instance, phosphorus's +5 oxidation state aligns with phosphoric acid \(\text{H}_{3}\text{PO}_{4}\), where the three hydrogens balance the oxidation state of phosphorus.

acidic solutions

Acidic solutions are formed when nonmetal oxides react with water. The resulting solution tends to have a lower pH and contain acids that release hydrogen ions \(\text{H}^+\) upon dissolution.
When nonmetal oxides react with water, the transformation involves molecular rearrangement that maintains the nonmetal’s oxidation state in the new acid.

• For instance, when phosphorus pentoxide reacts with water, orthophosphoric acid \(\text{H}_{3}\text{PO}_{4}\) is formed, exhibiting the strong acidic nature.
• Similarly, selenium dioxide forms selenous acid \(\text{H}_{2}\text{SeO}_{3}\), and boron trioxide yields boric acid \(\text{H}_{3}\text{BO}_{3}\), both contributing to the acidity due to their ability to release \(\text{H}^+\) ions.

Acids formed from nonmetal oxides like these are crucial for many industrial and biological processes. They are characterized by their ability to donate protons and influence chemical reactivity and solubility in solutions.