Using NaOH tests for CO2 ?

2007-02-09 6:48 am

In the test for carbon dioxide, calcium hydroxide is used. The limewater turns milky as calcium carbonate formed.
Can sodium hydroxide also be used to test for carbon dioxide? In biology, it is said that it can be used to absorb carbon dioxide. Therefore, is it suitable to test for the presence of carbon dioxide?
　　　2NaOH + CO2 → Na2CO3 + H2O
Some may say that sodium carbonate is soluble in water, if we boil the solution and weigh the mass increased. Can that be a test for CO2?

回答 (1)

N70

2007-02-09 8:18 am

✔ 最佳答案

The way of testing you mentioned is rather clumpsy and inconvenient. You can of course carry out a "test" in that way but it cannot give you any instant and visable indication and requires additional steps (boiling, weighting) and calculations. It could be a test but it certainly is not a good one.

Also, if you remember, there is a further proof for the presence of CO2 in using calcium hydroxide which NaOH cannot give -- The precipitate will redissolve in excess CO2 due to the formation of soluable salt calcium hydrogencarbonate:

CaCO3 (s) + CO2 (aq) + H2O (l) → Ca(HCO3)2 (aq)

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