Problem 3 - Chemical Principles in the Laboratory

Question

The name acetic anhydride implies that the compound will react with water to form acetic acid. Write the equation for the reaction.

Step-by-Step Solution

Answer

The balanced equation for the reaction of acetic anhydride with water to form acetic acid is: \[(CH_3CO)_2O + H_2O ⟶ 2 CH_3COOH\]

Step 1: Identifying the chemical formulas of the reactants and products involved

Acetic anhydride, as the name suggests, is the anhydrous form of acetic acid. Its chemical formula is (CH3CO)2O. Water's chemical formula is H2O. The product of the reaction will be acetic acid, which has the chemical formula CH3COOH.

Step 2: Writing the unbalanced equation

Let's first write the unbalanced equation by placing the reactants on the left side of the equation and the products on the right side. \[(CH_3CO)_2O + H_2O ⟶ CH_3COOH\]

Step 3: Balancing the equation

In order to balance the chemical equation, we need to ensure that the number of atoms of each element on both sides of the equation is equal. \[((CH_3CO)_2O + H_2O)] \Rightarrow [CH_3COOH]\] We notice that there are 4 carbon atoms, 6 hydrogen atoms, and 3 oxygen atoms on the left side, while there are only 2 carbon atoms, 4 hydrogen atoms, and 2 oxygen atoms on the right side. To balance the equation, we need to add coefficients in front of the chemical formulas: \[((CH_3CO)_2O + H_2O) ⟶ (2 CH_3COOH)\] Now, there are 4 carbon atoms, 6 hydrogen atoms, and 3 oxygen atoms on both sides of the equation. The balanced chemical equation for the reaction of acetic anhydride with water to form acetic acid is: \[(CH_3CO)_2O + H_2O ⟶ 2 CH_3COOH\]

Key Concepts

Chemical Formulas

Chemical formulas are shorthand representations of molecules using chemical symbols to convey the type and number of atoms in the compound. In the case of the reaction between acetic anhydride and water, we deal with the following chemical formulas:

• Acetic anhydride: \((CH_3CO)_2O\)
• Water: \(H_2O\)
• Acetic acid: \(CH_3COOH\)

These formulas help us understand the composition of each molecule. Acetic anhydride consists of two acetyl groups (\(CH_3CO\)) and one oxygen atom. Water consists of two hydrogen atoms and one oxygen atom, while acetic acid contains one acetyl group and one hydroxyl group (\(-OH\)).
Understanding these formulas is crucial because they serve as the basis for writing and balancing chemical equations in chemical reactions. Observing the formulas carefully allows us to deduce possible reactions and their respective products, as seen in the reaction that forms acetic acid from acetic anhydride and water.

Balancing Chemical Equations

Balancing chemical equations involves ensuring the number of atoms for each element is equal on both sides of the equation. This is necessary because of the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.
In our example, the unbalanced equation is:\[ (CH_3CO)_2O + H_2O ⟶ CH_3COOH \]Initially, the atom count is not equal on both sides:

• Left side: 4 carbons, 6 hydrogens, 3 oxygens
• Right side: 2 carbons, 4 hydrogens, 2 oxygens

To balance the equation, we adjust coefficients, leading to:\[ (CH_3CO)_2O + H_2O ⟶ 2 CH_3COOH \]Now, each element has the same number of atoms on both sides:

• 4 carbons
• 6 hydrogens
• 3 oxygens

This balanced equation accurately represents the reaction where acetic anhydride and water combine to produce two molecules of acetic acid, adhering to conservation laws.

Acetic Anhydride and Water Reaction

The reaction between acetic anhydride and water exemplifies a simple yet illustrative example of a hydrolysis reaction. In this reaction, acetic anhydride, a dehydrated form of acetic acid, reacts with water to form two molecules of acetic acid.This specific reaction can be represented in the balanced chemical equation:\[ (CH_3CO)_2O + H_2O ⟶ 2 CH_3COOH \]Here's how the process works:

• Acetic anhydride takes two \(CH_3CO\) groups and adds a water molecule to form two \(CH_3COOH\)
• This reaction is a typical example of hydrolysis, where a water molecule splits into hydrogen and hydroxide ions, facilitating the conversion of acetic anhydride into acetic acid.

Through this reaction, we not only obtain acetic acid but also see how chemical reactions can transform simple reactants into more complex molecules. Such transformations are commonly leveraged in chemical industries and laboratory synthesis processes.