Question

Using the Lewis concept of acids and bases, identify the Lewis acid and base in each of the following reactions:

Ni(NO3)3(s)+6H2O(l)→Ni(H2O)63+(aq)+3NO3−(aq)

Can someone explain to me why Ni(NO3)3 is a lewis acid if it's accepting h2o and why h2o is a lewis base if it's giving itself instead of receiving an e-?

CH3NH2(g)+HBr(g)→CH3NH3Br(s)

Can someone also explain to me why HBR is a lewis base it's donating a H+? And why CH3NH2 is a lewis acid for accepting a H+?

This concept is proving to stil be very confusing to me.

Answer 1

Lewis acids accept an electron pair and lewis bases donate electron pair.

In the first reaction, Ni³⁺ ion is the lewis acid as it accepts electron pairs from H₂O. Since H₂O donates the lone pair on oxygen atom to coordinate with Ni³⁺ ion, so it acts as the Lewis base.

In the second reaction, the lone pair on nitrogen atom of CH₃NH₂ is donated to the H⁺ obtained from HBr. So, according to the definition,CH₃NH₂ is the Lewis base as it donates electron pair and H⁺ is the Lewis acid as it accepts the electron pair from Nitrogen. Once CH₃NH₃⁺is formed it accepts electron pair from Br^- like a Lewis acid .Then Br^- is the Lewis base.