NH3 and CH3NH2 have Kb values of 1.8 x 10-5 and 5.0 x 10-4, respectively; which of the following statement(s) is (are) CORRECT?

(i) CH3NH2 is a stronger base than NH3.
(ii) the conjugate acid of CH3NH2 is a stronger acid than the conjugate acid of NH3.
(iii) 0.1 M aqueous solutions of CH3NH2 and NH3 have the same concentration of hydroxide ion, OH-.

i know i is true, but am not sure of the others

OK. If you know (i) is true (you're right), then you KNOW (III) can't possibly be right. Right? Because if CH3NH2 is a stronger base than NH3, then CH3NH2 must give a higher concn of OH^- than NH3. Now what about (ii)?

If CH3NH2 is a stronger base than NH3, then the conjugate acid of CH3NH2 must be weaker than the conjugate acid of NH3. By knowing (i) is right, you should be able to reason about the other two.

What is the H+ ion concentration of this solution?

A solution is made by dissolving 0.0112 g KOH in enough water to make 1.0 liter of solution. What is the H+ ion concentration of this solution?

a. ) 2.0 x 10-3 M
b. ) 8.0 x 10-2 M
c. ) 1.2 x 10-13 M
d. ) 5.0 x 10-11 M
e. ) 5.0 x 10-12 M

To determine the correctness of the statements, we need to compare the strengths of the bases NH3 and CH3NH2 based on their Kb values.

The strength of a base can be determined by its Kb value, where a higher Kb value indicates a stronger base. Therefore, comparing the Kb values of NH3 and CH3NH2:

- NH3 has a Kb value of 1.8 x 10^-5
- CH3NH2 has a Kb value of 5.0 x 10^-4

(i) CH3NH2 is a stronger base than NH3.
Since CH3NH2 has a higher Kb value than NH3, it can be concluded that statement (i) is correct. CH3NH2 is indeed a stronger base than NH3.

(ii) The conjugate acid of CH3NH2 is a stronger acid than the conjugate acid of NH3.
To determine the strength of the conjugate acids, we need to consider the reverse reaction. The stronger the base, the weaker its conjugate acid. Therefore, the conjugate acid of NH3 should be stronger than the conjugate acid of CH3NH2. Thus, statement (ii) is incorrect.

(iii) 0.1 M aqueous solutions of CH3NH2 and NH3 have the same concentration of hydroxide ion, OH-.
Kb values are used to calculate the concentration of hydroxide ions in a solution. So, a higher Kb value implies a higher concentration of OH- ions. Based on the given Kb values, CH3NH2 has a higher Kb value than NH3, indicating that CH3NH2 will have a higher concentration of OH- ions. Therefore, statement (iii) is incorrect.

In summary:
(i) CH3NH2 is a stronger base than NH3. [Correct]
(ii) The conjugate acid of CH3NH2 is a stronger acid than the conjugate acid of NH3. [Incorrect]
(iii) 0.1 M aqueous solutions of CH3NH2 and NH3 have the same concentration of hydroxide ion, OH-. [Incorrect]