[benr]

I don't know if this is H.S. or College level. I think I knew how to do this once (moles?), but it is now too long ago for me to remember.

A hobby chemical requires an acid auxiliary. The recommended acid is either 56% acetic acid or citric acid. I do not know the resulting pH but the formula specifies 3T acid in 2.5 gallons of water.

I want to substitute 20 degree baume muriatic acid/HCL (the container says 31.45% acid) for the acetic acid. Can someone calculate the acetic acid pH and tell me how much muriatic acid I should use to obtain the same pH as the acetic acid in the same amount of  water and how you arrived at the answer? Thanks.

[Borek]

3T acid in 2.5 gallons of water

T like tablespoon?

[benr]

Yes, T like Tablespoon. I assume you will have to calculate in metric and convert back or I can do that. Thanks.

[Borek]

Calculation of concentration and then calculation of pH would be not hard. However, acidifying the solution with HCl is not equivalent, as weak acids are much better at buffering the pH of the solution. Well, technically there are no buffers in the solution till part of the acid gets neutralized, but solution response (pH change) to the small amount of base will be very different.

[benr]

Thanks for your reply, but why would 56% acetic acid be considered a weak acid? Its pH is not far from 20 degree baume HCl at least on the pH scale anyway or does a small difference on the scale translate to a large difference since the scale is logarithmic?

[Borek]

Distinction between weak and strong acids has nothing to do with their concentrations, it is about their willingness to dissociate in water.