Problems with the reaction between calcium sulfide and sodium carbonate
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I have a few questions for the more experienced colleagues: I currently have calcium sulfide precipitate, and when it is added to sodium carbonate solution, calcium carbonate precipitate is formed – what else is produced? Sodium hydrosulfide or sodium sulfide? And will this reaction go to completion? How to distinguish between sodium hydrosulfide and sodium sulfide?
Um, I did some research. Calcium sulfide undergoes double hydrolysis; there should be hydrosulfide ions produced, so sodium hydrosulfide is formed, right? Could there be sodium sulfide? Secondly, given a bottle of solution, how do I know whether it is sodium hydrosulfide or sodium sulfide? Is there a detection method?
In the redox titration analysis of the sample, when the sulfur content corresponds to the proportion in sodium sulfide, it is considered to be sodium sulfide； When the sulfur content is lower than the sulfur proportion in sodium sulfide but higher than that in sodium hydrosulfide, it indicates that there may be sodium hydrosulfide present in the sodium sulfide. When the sulfur content reaches the proportion relative to the sulfur content in sodium hydrosulfide, it indicates that it is sodium hydrosulfide.
Um, what you said makes sense. I analyzed it from the root cause as well: calcium sulfide undergoes hydrolysis, producing hydrosulfide and hydroxide ions. After the calcium ions are consumed, these two ions react with each other to form sulfide ions. Therefore, the yellow liquid obtained should be sodium sulfide. It was just a small validation test. If it weren’t for the fact that the company’s instrument for detecting anions broke down, it wouldn’t have been such a hassle :P Thank you all!
Is there any hydrogen sulfide gas being produced?
The alkali metal and alkaline earth metal salts of sulfides are all basic; without adding sufficient acid, no hydrogen sulfide will be produced. However, due to the oxidative action of oxygen in the air, the color may darken; simultaneously, due to the acidic nature of the oxidation products, hydrogen sulfide odor may be released and detected.