# repost chemistry

posted by .

A student adds 1.00x10^-8 moles HCl to a liter of soln. The resulting soln will be acid, basic, neutral, or impossible to determine?

I believe that it is impossible to determine, because it does specify that the temperature was at 25*C. I know that a neutral pH deviates from 7 at any other temperature other than 25*C. If I assumed that the temperature is 25*C, I can calculate the pH=-log(1x10^-8)=8, which is basic.

Which of the species act as a Lewis acid: CH3CH2N or NO2?

I know that a Lewis acid is an electron acceptor. I think NO2, because one of its oxygen is missing an electron.

Lactic acid partially dissociates, Ka=1.4x10^-4, to form hydronium ions and conjugate base. Determine kb for this base.

kb=10^-14/ (1.4x10^-4)= 7.1x10^-11
Is that how I am supposed to do this?

Thanks for the help!

• repost chemistry -

The first is impossible to determine because it is not known what the solution was. If it was pH 2 before, it will be acid still. If it was pH 14 before, it will be base still.

NO2 is an electron donor, so it is a Lewis base. Nearly all Nitrogen compounds, valence 3, are bases.

Yes, Ka*Kb=1E-14