Chemical Engineering in Daily Life – Question 57: Why can’t scale be removed?
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If you put tap water in a shallow dish and let it evaporate naturally, add more water when the water level drops significantly; repeat this process several times to maintain a certain level of humidity in the room. If you return home after a few days away on a business trip and find that the water in the dish has completely evaporated, not a single drop left. At this point, you will find scale at the bottom. You can’t clean it even with a lot of water, nor can you use the stainless steel wire used for washing dishes (what’s its name? ) It can’t be taken down either. Even with a lot of vinegar, it can’t be cleaned properly. May I ask: why is this?
Happy weekend, teacher. -------------------------------- This is due to scaling. In the north, the water comes from groundwater and is hard, which causes this problem. In the south, the tap water comes from rivers and is soft, so there’s no such issue
Cleaning is a problem; I don’t know what method can be used to clean it thoroughly. Wait for the teacher to announce the answers: lol
The water quality is too hard, mainly due to high levels of calcium and magnesium. The precipitates formed from calcium and magnesium are primarily carbonates and sulfates; magnesium sulfate has a higher solubility and is therefore easier to remove. Carbonates can also be removed by reacting them with acetic acid, or using hydrochloric acid. Sulfates, on the other hand, are more difficult to remove. In such cases, soda water can be used for washing, along with heating. According to the solubility product rule, calcium carbonate is more soluble than calcium sulfate. By using the CO3 2- ion, sulfates can be converted into calcium carbonate, which is less soluble. This allows calcium carbonate to be removed using acids, thereby achieving the purpose of cleaning. This is my personal understanding; for more details, please consult relevant data. I would appreciate feedback from experts
As mentioned above, the water is too hard, and it has hardened inside the basin.