I'm studying the CO2 gas captured by NaOH solution as reaction below:
2NaOH (aq) + CO2 (g)= Na2CO3(aq) + H2O
As CO2 is continuously fed into NaOH solution, CO2 is continuously absorbed as reaction below:
Na2CO3 (aq) + CO2 (g) + H2O(l)= 2 NaHCO3 (aq)...
I'm interested to measure the concentration of carbonate and bicarbonate ion in this experiment.Could anybody suggest me how to measure those ions?
Tq
The pH will have an impact on the distribution of those ions.
Best method is ion chromatography since it does the separation and measures the concentration of both species.
Other tests include acidification to form CO2 gas or using test strips. http://www.galladechem.com/catalog/emd_teststrips/carbonate-hardness-test-strips-70-425-ppm-em-quant-1-pk-of-100.htm
Meassuring Alcalinity of the solution established by the equilibrium of chemical species in water by pH (CO2, HCO3-, CO3- - )
Thank you for your respond..
Kevin Hsieh...I have be informed from supplier that the test trips can test for carbonate as hardness parameters...Can you explain how to relate the hardness with concentration measurement...
Pablo...can you please explain more about your comment...TQ..
I'd suggest reading Chapters 1 and 2 of http://www.epoca-project.eu/index.php/guide-to-best-practices-for-ocean-acidification-research-and-data-reporting.html "Guide to best practices for ocean acidification". In my experience, test strips aren't going to give you any quantitatively useful information. I'd measure the pH and alkalinity (spectrophotometer / titration) and then calculate the bicarb and carb concentrations using CO2SYS http://cdiac.ornl.gov/oceans/co2rprt.html . Beware of pH probes, they typically don't perform reliably in ionic solutions. If you want useful (i.e., reproducible and reliable) results, you won't find a "simple" solution.
Based on your equation for the reaction, it is most likely that a probe test will not give you accurate result. This is because NaHCO3 is most stable at ambient condition and your Na2CO3 reaction route is temperature guided. CO2 concentration must be calculated using molar concentration ration of the reactant. CO2 depletion is then evaluated by measuring the reaction rate based on molar ratio of NaOH and CO2.used. This is the best approximation at constant temperature.
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