Based on the relative stability of the conjugate acids, which of the following bases has the largest value for Kb?
a. CH3NH2
b. NH2NH2
c. HONH2
d. ClNH2
Do you have the stabilility of the conjugate acids somwhere? What are they?
Kb = Kw/Ka so if you have the Ka value for each of those listed you can calculate Kb. Then you can compare the Kb values.
a
To determine which base has the largest value for Kb based on the relative stability of their conjugate acids, we can analyze the relative strengths of these acids.
The strength of an acid is determined by its ability to donate a proton (H+). In this case, it is determined by the stability of the conjugate base formed after the acid donates its proton.
To determine the relative stability, we can compare the electronegativities and resonance effects in the conjugate bases.
Let's analyze the options:
a. CH3NH2
The conjugate acid of CH3NH2 is CH3NH3+. In this case, the nitrogen atom is bonded to three hydrogen atoms and one carbon atom. The carbon atom donates electron density, which increases the stability of the conjugate acid.
b. NH2NH2
The conjugate acid of NH2NH2 is NH3NH3+. Here, both nitrogen atoms are bonded to three hydrogen atoms, and there is no electron-donating effect from other atoms.
c. HONH2
The conjugate acid of HONH2 is HONH3+. In this case, only one hydrogen atom is bonded to the nitrogen atom, and there is no electron-donating effect from other atoms.
d. ClNH2
The conjugate acid of ClNH2 is ClNH3+. The chlorine atom is more electronegative than nitrogen, which withdraws electron density and decreases the stability of the conjugate acid.
Based on this analysis, we can determine that the base with the largest value for Kb (and thus the most stable conjugate acid) is option a. CH3NH2.
To answer this question, we need to determine the relative stability of the conjugate acids of each base. The stability of a conjugate acid can be determined by examining the strength of the bond formation between the proton (H+) and the conjugate base.
The larger the bond strength, the more stable the conjugate acid, and the stronger the base is. Therefore, the base with the largest value for Kb will have the most stable conjugate acid.
Let's analyze each option:
a. CH3NH2: The conjugate acid is CH3NH3+. The positively charged nitrogen atom has a partial positive charge due to the addition of the proton. The nitrogen in CH3NH2 has an electron-donating methyl group which enhances the electron density around the nitrogen atom. This increases the stability of the conjugate acid.
b. NH2NH2: The conjugate acid is NH3NH3+. The presence of two nitrogen atoms increases the delocalization of the positive charge, making it more stable than the conjugate acid of CH3NH2.
c. HONH2: The conjugate acid is H2NONH3+. The presence of an oxygen atom in HONH2 enhances the electron density around the central nitrogen atom. This stabilizes the positive charge on the conjugate acid, making it more stable than the conjugate acids in options a and b.
d. ClNH2: The conjugate acid is ClNH3+. In this case, the chlorine atom is more electronegative than nitrogen, causing the positive charge to be more localized on the nitrogen atom. This reduces the stability of the conjugate acid compared to the other options.
Considering the explanations above, it can be concluded that option c, HONH2, will have the largest value for Kb as its conjugate acid is the most stable among the given bases.