A base has a Kb of 2.5 x 10–11. Which of the following statements is true?

This is a concentrated base.

This base ionizes slightly in aqueous solution.

This is a strong base.

An aqueous solution of this base would be acidic.

To determine which of the statements is true, we need to understand the concept of base strength and the relationship between the base dissociation constant (Kb) and the strength of a base.

The base dissociation constant (Kb) is a measure of the strength of a base. It quantifies the extent to which a base dissociates or ionizes in an aqueous solution. The larger the value of Kb, the stronger the base, and the more it ionizes in solution.

Now let's analyze the given Kb value of 2.5 x 10–11:

1. "This is a concentrated base."
The concentration of a base refers to the amount of the base present in a given volume of solution. The given information only provides the base dissociation constant (Kb) and does not provide any information about the concentration. Therefore, we cannot conclude whether the base is concentrated or not based on the given Kb value. Hence, this statement is not necessarily true.

2. "This base ionizes slightly in aqueous solution."
The base dissociation constant (Kb) quantifies the extent of ionization of a base in an aqueous solution. Since the given Kb value is relatively small (2.5 x 10–11), we can infer that the base does not ionize significantly in solution. Hence, this statement is true.

3. "This is a strong base."
As mentioned earlier, the base strength depends on the value of the base dissociation constant (Kb). Since the given Kb value (2.5 x 10–11) is relatively small, it indicates that the base is not strong. Strong bases typically have Kb values greater than 1, while the given value is much smaller. Hence, this statement is not true.

4. "An aqueous solution of this base would be acidic."
The basicity or acidity of a solution depends on the nature of the solute. Bases typically produce hydroxide ions (OH-) when dissolved in water, resulting in an alkaline or basic solution. Since the question states that the compound is a base and has a Kb value, we can conclude that an aqueous solution of this base would be basic, not acidic. Hence, this statement is not true.

In conclusion, the correct statement is: "This base ionizes slightly in aqueous solution."

The statement "This base ionizes slightly in aqueous solution" is true.

The value of Kb, or base dissociation constant, indicates how much a base ionizes or dissociates in water. A smaller value of Kb suggests that the base ionizes only slightly in aqueous solution, meaning it does not completely dissociate into ions.

In this case, since the given Kb value is small (2.5 x 10–11), it indicates that the base ionizes only to a small extent in water. Therefore, the statement "This base ionizes slightly in aqueous solution" is true.

We don't know how concentrated the base is; the concentration is not stated in the problems.

It has a Kb of 2.5E-11; therefore, #2 is correct. #1 COULD be correct under the right conditions.