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a. Reaction of $\ce{CO2}$ addition in water is as follows:

$\ce{CO2}$ + $\ce{H2O}$ $\ce{->}$ $\ce{H2CO3}$

b. Then, pH of $\ce{H2CO3}$ solution is increased to 12 by addition of 1M $\ce{NaOH}$.

So, the reaction would be:

$\ce{2NaOH(aq)}$ + $\ce{H2CO3(aq)}$ $\ce{->}$ $\ce{Na2CO3(aq)}$ + $\ce{2H2O}$

c. This new solution at pH 12 is added to $\ce{CaCl2}$ solution; the final reaction of the system would be:

( $\ce{Na2CO3(aq)}$ + $\ce{2H+}$ + $\ce{2OH-}$ ) + $\ce{CaCl2}$ $\ce{->}$ $\ce{CaCO3(s)}$ + $\ce{2 NaCl}$ + $\ce{2H2O}$

My questions are:

1. Is the final chemical reaction correct?

2. By setting the pH of step c equal to 12, which is ( $\ce{Na2CO3(aq)}$ + $\ce{2H+}$ + $\ce{2OH-}$ ), and addition of 50 ml of that to $\ce{CaCl2}$ solution, is it possible to make some sort of pH calculations?

$\ce{[H+]} = 10^{-12} M$

$\ce{[OH-]} = 10^{-2} M$

$\ce{[CO3]}$ = assuming 0.05 M in 50 ml

3. Overall, is it possible to do a numerical simulation (e.g., MATLAB) of change in the overall solution pH? OR, predict the final pH by calculations?

Thanks and Best Regards,

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  • $\begingroup$ This can't bu done precisely, as long as you don't know how much CO2 was dissolved. Still difference between cases should be negligible as long as you add surplus of CaCl2. $\endgroup$ – Mithoron Aug 16 at 18:26
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As an answer to your overall question: it is indeed possible to do numerical simulations of pH in different solutions or mixtures, and there is a number of programs or spreadsheets available if ou search the net. My personal favorite is Curtipot made by Prof. Gutz: http://www.iq.usp.br/gutz/Curtipot_.html

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