[vJames]

Hi all,

We've been doing equilibrium for a couple of weeks and have just started on weak acids.

We just covered ionization constants (K_a) and I'm stuck on a few problems that I've been given.

1. Find the value of K_a of an acid if a 2.00 M solution has a hydrogen ion concentration [H⁺] of 0.14 M

2. Find the K_a in a 0.31 M HOCl solution which has a [H⁺] = 1.0 × 10^-4 M.

I knew my teacher was busy when he gathered these questions at the last minute and I actually found them online somewhere so I'm not sure if the questions are wrong or not (they are every now and then).

The previous ones were similar but gave me the ionization constant and I had to work to find the concentration of hydrogen ions or such using ICE tables.

Without thinking I drew up some ICE tables for these questions and the equilibrium equation for the second problem but then I realised I didn't know where to go from there.

[vJames]

Ahh, I've figured it out.

I was confused by the wording. The acid concentrations are initial and it is assumed that there is no dissociation. The hydrogen ion concentrations are the concentrations after dissociation when the ions are in equilibrium.

For future reference, is it possible to delete the thread I started? I was trying to find a way to do so as soon as I realised my mistake as I don't want the thread to waste space or people's time.

[billnotgatez]

Actually, this provided a learning experience for all.

and

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