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As stated in my previous answer on precipitation, formation of precipitates in supercritical is a common issue. Ask those who do sub/supercritical fluid chromatography. Sometimes you inject a methanol soluble compound into a chromatography column and the mobile phase is supercritical carbon dioxide (often mixed with a small amount of methanol) and the ...


4

As a brief recap, when calling such reaction a "molecular equation", we are supposed to forget that the empirical formulas for ionic substances refer to formula units, not molecules. We treat all components as if they were molecules. The quirk with "molecular equation" lies within the willful ignorance striving for a simplification in ...


4

In "chemistry", we generally have a good idea of what we mean by precipitation: something falls down out of a liquid and we filter it off. Then we extend the definition to meteorology for rain falling out of the sky. And although precipitation in solids has been mentioned, its importance has not. Well, maybe because much of the solid precipitation ...


4

First iron(II) hydroxide $\ce{Fe(OH)2}$ is a precipitate made in aqueous solution, and it does not react with ammonia. Second, the iron(II) hydroxide $\ce{Fe(OH)2}$ is a green substance which is extremely sensitive to the oxygen of the air. In a couple of minutes, it gets brown, due to the formation of iron(III) hydroxide $\ce{Fe(OH)3}$ according to $$\ce{4 ...


4

In chemistry, on Earth in gravity, if a material from solution conformally, over all surfaces vertical and horizontal (e.g. the sides as well as the bottom of a container) is that still sometimes considered precipitation? Or is that crystallization from solution, and analogous to frost formation but not snow or rain? Precipitation, as typically used an ...


3

This topic and the related one in your other question had 2 aspects: phenomenological and terminological ones. Meteorological and chemical precipitation are different phenomena. The former is the water phase change from gas to liquid or solid, that is (almost) independent on air presence, with vapour saturated pressure criteria, usually considered in ...


3

First, my answer here is relevant: What is chemical formula of Bauxite?, and also follow links inside. Regarding your question specifically, there is not much difference. However, there are some conventions that come into play here. The three formulae describe compounds that stoichiometrically have four atoms of oxygen and hydrogen for each atom of silicon. $...


3

would it be possible to dissolve silver chloride just by adding another, more insoluble salt? For example: $$\ce{AgCl(s) + NaBr(aq) -> AgBr(s) + NaCl(aq)}$$ It is possible to get the chloride ion back into solution by adding NaBr. The effect is to lower the silver ion concentration so drastically that chloride goes back into solution. This kind of ...


2

$\ce{BaSO4}$ is insoluble in dilute solutions of acids, because this dissolution would produce the following ions in solution : $\ce{Ba^{2+}, H^+}$ and $\ce{SO4^{2-}}$. And the preceding reaction has shown that $\ce{Ba^{2+}}$ and $\ce{SO4^{2-}}$ cannot exist simultaneously in solution : they must react to produce a precipitate of $\ce{BaSO4}$. On the other ...


2

The ion $\ce{CO3^{2-}}$ introduced in the first reaction must be produced by dissolving a soluble carbonate like $\ce{Na2CO3}$. On the other hand $\ce{BaCl2}$ or $\ce{CaCl2}$ have to be dissolved in water to react. If they are introduced as solid these substances will not react, unless they slowly get dissolved. Nobody really knows why these chlorides are ...


1

On writing the equations for the initial precipitation and the dissolution reactions, it can be seen that their equilibrium constants are not the same. Taking $K_1,K_2$, and $K_3$ to be the constants for each of these and the double dissociation of $\ce{H2CO3}$ respectively, you get $$K_2=\frac{1}{K_1K_3} \neq K_1$$ This is why you can't reason out that the ...


1

The stability constant of $\ce{Pb−EDTA}$ complex is $\ce{10^{18}}$, which is huge. The solubility product of $\ce{PbSO_4}$ is $10^{−8}$ , which cannot be compared to the effect of $\ce{EDTA}$. So the precipitate $\ce{PbSO4}$ must be soluble in $\ce{EDTA}$ solutions. These numerical data have been taken from J. G. Stark, Chemistry Data Book, John Murray, ...


1

Why do reusable heat packs have a limited time frame before the reaction becomes irreversible? This reaction should never become irreversible until and unless there is bacterial growth or loss of water for some reasons. For example, one manufacturer explains that the pads can re-used for 18 years! http://www.thermo-pad.com/frequently-asked-questions/ We ...


1

The sodium acetate that shows this behavior is not anhydrous $\ce{NaCH3COO}$ as you write. It is the hydrated salt $\ce{NaCH3COO·3H2O}$. The anhydrous salt does not show the phenomena of surfusion. Only the hydrated form does it. If you keep the solid form of the hydrated salt a long time, I think it will slowly loose water by evaporation through the plastic ...


1

It is supposed addition of solid $\ce{Na2CrO4}$ would cause negligible volume change, so we can afford to consider the same $[\ce{Sr^2+}]$ as the initial one. The task is rather theoretical, supposing the time point when $\ce{[Sr^2+][CrO4^2-]}$ just reached $K_\mathrm{sp,\ce{SrCrO4}}$, while $K_\mathrm{sp,\ce{SrCrO4}}$ and $\ce{[Sr^2+]}$ are given. The ...


1

Solutions of aluminum sulfate are highly acidic. The Merck Index states that at a concentration $0.2 M$, the pH is $3.0$.


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