Can we use a chemical thử nghiệm lớn distinguish between $ceNa2CO3$ và $ceNaHCO3$?
I know that $ceNaHCO3$ can be thermal decomposed into lớn $ceNa2CO3$ via this reaction: $2ceNaHCO3-> ceNa2CO3 + ceCO2 + ceH2O$However, I am not sure if thermal decomposition is a chemical test.
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Heating salternative text is an important kiểm tra in determining the anion in the salternative text by checking the gas evolved. This test is called dry heating test & is a important part of qualitative analysis of salt. But this thử nghiệm goes under physical examination of salt (checking color, appearence etc.).
One important chemical demo khổng lồ differentiate carbonate và bicarbonate is $ceMgSO4$ chạy thử.
$$ceNa2CO3 + Mg^2+ -> MgCO3↓(white) + Na+$$
$$ceNaHCO3 + Mg^2+ -> MgCO3↓(white) + H2O + CO2 ^$$
When carbonate salternative text is reacted with $ceMgSO4$, a Trắng salt precipited while bicarbonate salternative text on reacting with $ceMgSO4$, not only a Trắng salt precipited but also a brisk effervescence occur. The gas is detected by passing it through lime water.
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answered Jul 19, năm 2016 at 7:49
Nilay GhoshNilay Ghosh
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depends on your equipment. You can estimate the amount of $ceNaHCO3$ by taking a known amount of sample, heating it to $simpu300 °C$, cooling it khổng lồ room temperature & measuring the weight again. Zero loss means 100% $ceNa2CO3$. Loss of $37\%$ of weight means $100\%$ $ceNaHCO3$. The dependence is linear within $0-37\%$ weight loss.
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Better way is to react a gram of material with $ceHCl$, skết thúc forming $ceCO2$ through saturated $ceBa(OH)2$ ($ceCa(OH)2$ can be used, but wouldn"t work as well), collect, wash dry và weight the precipitate $ceBaCO3$. Both experiments tell you how much carbonate anion you have sầu in a sample. You have lớn assume that $ceNaHCO3$ and $ceNa2CO3$ were the only components in the mix.
You can also evaluate the ratio based on pH of the resulting solution if you know how to calculate pH for buffers.
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edited Feb 10, 2019 at 17:16
andselisk♦
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answered Jul 18, năm nhâm thìn at 16:59
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As you mentioned in your post, thermal decomposition and measurement of the resulting gas would be one way lớn distinguish what you have. I would Call this a physical, rather than chemical method, however.
This kind of thermal decomposition isn"t something most labs would consider for two reasons:
Both chemicals are cheap. They"re generally bought by the kilo & looking at what we get charged for them the company is basically only charging us for the cost of the containers và shipping.
Thermal decomposition & gas measurement is, nowadays at least, a fairly specialised technique. Most labs would struggle to piece together the required equipment & even if they could find it, would likely be reluctant lớn vì chưng so.
That said, your question seems purely academic rather than practical, so lets consider a possible chemical method.
Sodium carbonate is well known for its use in inorganic analysis, as it reacts with certain metals lớn give carbonate salts of well defined colour.
The chạy thử can distinguish between copper (Cu), iron (Fe), và calcium (Ca), zinch (Zn) or lead (Pb). Sodium carbonate solution is added to lớn the salt of the metal. A xanh precipitate indicates Cu2+ ion. A dirty green precipitate indicates Fe2+ ion. A yellow-brown precipitate indicates Fe3+ ion. A White precipitate indicates Ca2+, Zn2+, or Pb2+ ion. (Source: Wikipedia)
IIRC the demo doesn"t work with sodium bicarbonate, & as such you could use the reactions with a cheap metal such as iron lớn determine whether you had sodium bicarbonate or sodium carbonate.