Determining relative strength of acids and bases

[Annika_Karody_3L]

I wanted to clarify the justification for the classification of certain compounds as weak acids or bases.

Is the compound CH3NH3Cl, an acid because it cannot acquire any more protons, as made evident by its lewis structure,and would thereby donate protons in H2O? Furthermore, is it weak because it is a derivative of acetic acid?

Is the compound C6H5NH2 a base because an H+ can attach to the N, as observed from the lewis structure?

Thanks in advance for your help!!

[Anne Cam 3A]

CH3NH3Cl is an ionic compound, consisting of CH3NH3+ and Cl- ions. The overall salt does not donate protons, the CH3NH3+ ion does (to form H3O+) when the salt is dissociated in water. Cl- is a very weak conjugate base so its basicity is negligible. Therefore the salt is acidic because of CH3NH3+, a Bronsted acid.

Yes, C6H5NH2 is a base because the N atom can accept another proton. It would thus be a Bronsted base (accepts proton) and Lewis base (donates e- pair).

Hope this helps!

[Annika_Karody_3L]

That does, thank you!

What I meant to ask in the first part of my question was whether the cation is an acid because it cannot accept any more protons, but I realize now that it is positively charged, which also indicates that it can donate and H+ and form H3O+, so I think I'm good on that one. Thanks again for your help!

[Nancy Yao]

CH3NH3Cl is an ionic compound, consisting of CH3NH3+ and Cl- ions. The overall salt does not donate protons, the CH3NH3+ ion does (to form H3O+) when the salt is dissociated in water. Cl- is a very weak conjugate base so its basicity is negligible. Therefore the salt is acidic because of CH3NH3+, a Bronsted acid.

Yes, C6H5NH2 is a base because the N atom can accept another proton. It would thus be a Bronsted base (accepts proton) and Lewis base (donates e- pair).

Hope this helps!

This helps so much as I am doing the worksheet.

[Isabel Luu 1I]

Does anyone have any tips for gaining intuition about if a compound is basic or acidic? I am still struggling with figuring out the difference just by looking at the chemical formula.