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So, I wanted to make calcium acetate, through the reaction of calcium carbonate and vinegar.

My proposed reaction:

$$\ce{2CH3COOH(aq) + CaCO3(aq) -> Ca(CH3COO)2(aq) + CO2(g) + H2O(l)}$$

It seems that there is not much reaction between the chalk (source of $\ce{CaCO3}$ and the vinegar (source of acetic acid), except intermittent particles of chalk floating to the top.

The vinegar I am using is white distilled vinegar, with a $95\%$ concentration. I diluted it because the amount of chalks I would be using would not fit the amount of vinegar that would come from the $95\%$ solution.

Quantitatively, I'm using $11.4~\mathrm{ml}$ of vinegar (before dilution), and $11.4~\mathrm{g}$ of chalk. I have left it for over a day, but still there has not been much apparent progress.

What should I do? I tried heating up the solution in hopes of increasing the rate of reaction, but calcium acetate is less soluble in hot water than in cold water.

I do not want to precipitate the calcium acetate out of the solution, and onto the calcium carbonate sediment at the bottom.

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  • $\begingroup$ Calcium carbonate reacts with acids (including vinegar) quite readily and visibly. This means that at least one of your reactants is not what you think it is. $\endgroup$
    – Ivan Neretin
    Oct 23, 2016 at 8:46
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    $\begingroup$ Are you taking into account that vinegar only contains 4 to 8% of acetic acid? $\endgroup$
    – Variax
    Oct 24, 2016 at 13:19
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    $\begingroup$ en.wikipedia.org/wiki/Vinegar#Distilled $\endgroup$
    – Variax
    Oct 25, 2016 at 8:42
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    $\begingroup$ I am strongly suspicious that you have 95% acetic acid. That would be very close to glacial, and that's certainly not how vinegar comes at the store. $\endgroup$
    – Zhe
    Oct 25, 2016 at 18:26
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    $\begingroup$ @Variax Good finding - "distilled" vinegar has 5-8 % and after dilution it may be too weakly acidic. Also only 95 % in shop is alcohol ;) $\endgroup$
    – Mithoron
    Oct 25, 2016 at 19:18

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I am assuming by chalk you meant you were using blackboard chalk. In which case Ivan's comment was close, but all the other comments have completely missed the issue. The reason you saw no reaction is because chalkboard chalk isn't actually chalk, it is typically gypsum which is chemically calcium sulfate ($\ce{CaSO4}$) which is inert to acid. Chalk the mineral is calcium carbonate and chalkboard chalk used to be made from this, but today the sticks for writing are made of gypsum. Calling them chalk is a holdover from the old days.

I too fell for this trap many years ago.

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  • $\begingroup$ So what other source of calcium carbonate would be better? Maybe some egg shells or sea shells? $\endgroup$
    – SasQ
    Feb 28, 2022 at 12:40

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