Question

The ionization constant of a base is \(\frac{1}{10} .\) The base is described as (1) Normal base (2) Strong basc (3) Weak base (4) None of these

Short answer

Option (3) Weak base

Step-by-step solution

- Understanding the ionization constant

The ionization constant (also known as the base dissociation constant) is a measure of the strength of a base in solution. It tells us how well the base dissociates into its ions in water.

- Analyze the given value

In this problem, the ionization constant of the base is given as \(\frac{1}{10}\) which is equal to 0.1.

- Determine the strength of the base

A strong base typically has a high ionization constant, close to 1 or above. A weak base has a low ionization constant, usually much less than 1. Given that 0.1 is much less than 1, this base is considered weak.

- Choose the correct option

Based on the information, the base with an ionization constant of 0.1 is classified as a weak base. Therefore, the correct option is (3) Weak base.

Key concepts

base dissociation constant

The base dissociation constant (often represented as Kb) helps us understand how well a base ionizes in water. When a base dissolves in water, it splits into ions. The base dissociation constant measures the extent of this ionization.

For example, when ammonia (NH\textsubscript{3}) dissolves in water, it partially turns into ammonium (\text{NH\textsubscript{4}\textsuperscript{+}}) and hydroxide ions (\text{OH\textsuperscript{-}}). The formula for the base dissociation constant is:

\[ K_b = \frac{[\text{products}]}{[\text{reactants}]} \]
Replacing 'products' and 'reactants' with the actual concentrations, for ammonia it would be:

\[ K_b = \frac{[\text{NH\textsubscript{4}\textsuperscript{+}}] [\text{OH\textsuperscript{-}}]}{[\text{NH\textsubscript{3}}]} \]
A high Kb value indicates a strong base, as it ionizes completely in water. Conversely, a low Kb value shows a weak base, meaning only a small fraction of the base ionizes in water.

acid-base strength

Understanding the strength of acids and bases is crucial for their identification and use. For bases, the strength is determined by their ionization in water.

• Strong Bases: These are bases that ionize almost completely in water. They have a high Kb value, often close to or greater than 1.
• Weak Bases: These bases only partially ionize in water. They have a much lower Kb value, usually significantly less than 1.

Why does this matter? Strong bases, like sodium hydroxide (NaOH), are very effective at increasing the pH of solutions. They can be used in processes requiring high pH levels.

Weak bases, such as ammonia (NH3), are less aggressive but very useful when a milder effect is needed. It's essential to know whether a base is strong or weak before using it in chemical reactions or processes.

weak base

A weak base is a substance that only partially ionizes in water. This means that, even when a weak base is present in water, only a small percentage of its molecules dissociate to form ions. The rest of the base exists in its original form.

Common examples of weak bases include:

• Ammonia (NH3)
• Pyridine (C5H5N)
• Ammonium Hydroxide (NH4OH)

Weak bases have a relatively low Kb value, indicating their limited ionization. For instance, the Kb for ammonia is approximately 1.8 x 10^-5, which is much less than 1, showing it is a weak base.

When solving problems involving weak bases, always consider the ionization constant. Combined with the concentration of the base, this will help determine the degree of ionization and the resulting pH of the solution.