Phenol, C6H5OH, has a Ka of 1.3 * 10^-10. (c) Is phenol a stronger or weaker acid than water?

Verified step by step guidance

Step 1: Understand the concept of acid strength. Acid strength is determined by the acid dissociation constant, Ka. A larger Ka value indicates a stronger acid, as it implies a greater tendency to donate protons.

Step 2: Identify the Ka value for water. The self-ionization of water has a Ka value of approximately 1.0 * 10^-14 at 25°C.

Step 3: Compare the Ka values of phenol and water. Phenol has a Ka of 1.3 * 10^-10, which is larger than the Ka of water (1.0 * 10^-14).

Step 4: Analyze the comparison. Since phenol's Ka is larger than that of water, phenol is a stronger acid than water.

Step 5: Conclude based on the comparison. Phenol, with its higher Ka value, is a stronger acid than water, meaning it donates protons more readily than water does.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid Dissociation Constant (Ka)

The acid dissociation constant, Ka, quantifies the strength of an acid in solution. It is defined as the equilibrium constant for the dissociation of an acid into its conjugate base and a proton. A higher Ka value indicates a stronger acid, as it means the acid dissociates more completely in solution.

Comparative Acidity

To compare the acidity of two substances, one can look at their respective Ka values. Water has a very low dissociation constant (Kw = 1.0 x 10^-14 at 25°C), which indicates it is a weak acid. By comparing the Ka of phenol (1.3 x 10^-10) to that of water, we can determine which is the stronger acid based on their ability to donate protons.

Proton Donation

The strength of an acid is often assessed by its ability to donate protons (H+ ions) in solution. Phenol, with its hydroxyl group (-OH), can donate a proton, but its dissociation is limited compared to stronger acids. Understanding the mechanism of proton donation helps in evaluating the relative acidity of phenol and water.

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