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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: jordaann.t on August 06, 2019, 08:41:01 PM

Title: Calculating the pH of a mixture
Post by: jordaann.t on August 06, 2019, 08:41:01 PM

Hey everyone, not sure how to answer this question ... attached is the question and what I have tried. Thanks.

Title: Re: Calculating the pH of a mixture
Post by: chenbeier on August 07, 2019, 01:54:54 AM

Acetic acid is a weak acid. You habe to use the Formula for weak acids to  get the concentration. You can calculate the moles of calciumhydroxide and compare how much you have after neutralization. Maybe have to use the Henderson Hasselbalch equation

Title: Re: Calculating the pH of a mixture
Post by: Enthalpy on August 13, 2019, 06:08:58 AM

Can acetic acid reach a pH of 1.30 at all? I didn't grasp it properly I guess.

Pure acetic acid weighs 1049g/L and 60.05g/mol, that is, 1L contains 17.5mol.

At 1M the dissociation is only 0.4% and this decreases at higher concentration. So even with little water (which would introduce other limits), 1L and 17.5mol would contain less than 0.07mol H⁺. This gives a pH less strong than 1.16. I suppose the lesser dissociation doesn't let reach 1.30.

From measured pH=2.4 at 1M, pH=1.3 would need over 10× more concentrated H⁺ and then the ionization of the acid would be over 10× less, rather 0.04% than 0.4%, putting pH=1.3 out of reach.