Chemistry Weekly Newsletter - Monday, February 29, 2016

Top new questions this week: Why does CaCO3 react with HCl, but not with H2SO4? I have a wonderful reaction of marble chips, $\ce{CaCO3}$, with hydrochloric acid, $\ce{HCl}$, and carbon dioxide was released beautifully (fast, large volume, easy to measure and makes good visual ... acid-base reaction   asked by Sleepy Hollow 22 votes answered by Klaus Warzecha 42 votes What does the circle in a drawing of benzene ring represent? Does the cycle in the benzene ring represents double bonds' movement between the carbon atoms or free electrons movement? organic-chemistry molecular-structure notation   asked by studentrr 16 votes answered by Ivan Neretin 32 votes Why is a S-S bond stronger than an O-O bond? I'm wondering why exactly the single bond between two sulfur atoms is stronger than that of two oxygen atoms. According to this page, an $\ce{O-O}$ bond has an enthalpy of $142 \rm~\frac{kJ}{mol}$, ... inorganic-chemistry bond molecules   asked by IͶΔ 10 votes answered by user1825567 0 votes Why hydrofluoric acid (HF) has two Raman bands? Hydrofluoric acid ($\ce{HF}$) is a diatomic molecule with only one vibrational coordinate. Therefore I would expect only one Raman band, however there are two. Why? (source) raman   asked by Sparkler 8 votes answered by jheindel 3 votes What does dl- mean in nomenclature I came across the compound dl-stilbene dibromide, and I am confused by exactly what this means. I thought it might have meant a racemic mixture but there is only one chemical structure given. organic-chemistry nomenclature   asked by ringo 8 votes answered by DGS 8 votes Do bare protons exist, even transiently, in aqueous solution? Generally $\ce{H^+}$ ions in water remain in the form of hydronium ions ($\ce{H3O+}$), and not as "free" aqueous protons, as far as I've been taught. My question: is this always the case, even when ... inorganic-chemistry physical-chemistry computational-chemistry   asked by Sangkha Borah 8 votes answered by DavePhD 5 votes E1 and E2 elimination reactions of isotopically labeled bromocyclohexanes I am asked to draw the product for the E2 and E1 mechanism of 1,1-dibromo-2-methylcyclohexane. However one of the bromine atoms is the 79 isotope and the other is the 81 isotope. I am ... organic-chemistry homework reaction-mechanism isotope   asked by Nanoputian 8 votes answered by jerepierre 6 votes Greatest hits from previous weeks: What is a neutral atom? Someone gave me definition of atomic number as follows: The number of electron or proton present in a neutral atom is called atomic number. It is represented by Z. What does neutral mean here? ... atoms terminology   asked by Santosh Kumar 7 votes answered by geisshirt 15 votes Different reactions of clean and rusty iron nails in vinegar (acetic acid) I have submerged a iron nail in vinegar twice recently. What is puzzling me is the different results each time. The first time I submerged it, it was covered in rust. When I put it in the solution of ... home-experiment hydrogen   asked by user2514631 3 votes answered by kaliaden 3 votes Can you answer these? Trends in the covalency of bonding across the transition metals I am under the impression that the covalent character in the bonding of transition metal compounds increases across a group; in fact I think this is why they're called transition metals (a transition ... transition-metals periodic-trends organometallic-compounds   asked by RobChem 3 votes How is the reaction between Aluminium and Mercury Chloride possible? Aluminium is coated with a thin layer of Aluminium Oxide. Why then do we write the reaction as $$\ce{2Al + 3HgCl2 → 2AlCl3 + 3Hg}$$ Shouldn't we first write an equation showing how $\ce{HgCl2}$ ... reaction-mechanism   asked by CopperKettle 3 votes Improving efficiency of absorption refrigerator (ammonia+hydrogen) Apologies if this is not the right forum for this question, I checked the Physics side and there's no questions on this, whereas there's at least one other question here about absorption ... thermodynamics solubility absorption   asked by John U 3 votes

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