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Chlorine is more stable in ion state than in the neutral atom. But it is only more stable with respect to its own electrons. For the rest of the world it has one negative charge in excess. So, stable or not, it attracts positive charges like Na+ or any other positive ion. You cannot avoid that it will produce neutral assemblies of atoms, like NaCl. It is not ...

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The calcium amount may change from one fruit to the next one, or from one day to another one, or from one field to another one. 20 % is not a significant difference between such a measurement and another one. And this may happen for any constituant, not specially for calcium.

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The oxidation number of oxygen in carbonate anion is -2, as formally: $$\ce{CO3^2- -> C^4+ + 3 O^2-}$$ On the other hand, the oxidation number of oxygen in the superoxide KO2 is -1/2. As it is the average of sharing 1 electron between 2 atoms, formally: $$\ce{KO2 -> K+ + 2 O^{-1/2}}$$

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One can also say that any equilibrium constant $K$ is related to the change of free enthalpy ${\Delta G°}$ of the particular reaction : $${\Delta G° = RT lnK}$$ And this ${\Delta G°}$ does not depend on any other compound present in the solution.

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The equilibrium reaction for the auto-dissociation of water is: $$2\text{ H}_2 \text{O}(l) \leftarrow \rightarrow \text{H}_3\text{O}^+(aq) + \text{OH}^-(aq)$$ The associated equilibrium constant $K_w$ is: $$K_w=[\text{H}_3\text{O}^+]\times [\text{OH}^-] \approx 10^{-14}$$ (Strictly speaking the expression is: \frac{[\text{H}_3\text{O}^+]\times [\text{OH}^-...

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Perchloride is a word that has been used 100 years ago in the expression Iron perchloride to describe the Iron(III) chloride $FeCl_3$, so as to avoid any risk of confusion with the more usual Iron(II) chloride $FeCl_2$ which is obtained in the reaction of Hydrochloric acid with metallic iron. This prefix shows that there is more $Cl$ atom in $FeCl_3$ than in ...

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You can indeed "harden" glass by exchanging ions on the surface, but not because it turns into quartz glass. Quartz glass is mostly so robust because it has an extremely small thermal expansion coefficient, and is therefore mostly free of internal stress due to uneven cooling. Ordinary glass already gets a lot more durable when you temper it, thereby ...

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You could dealkalize the surface of a borosilicate glass to get rid of alkali ions, but I'm not aware of a method that allowed the extraction of alkali metals from the bulk of the glass. There are probably quite a few ways to modify the surface, but here's a few reported by Yashchishin and Zheplinskii [1]: Sulfur anhydride or Freon is the most widely ...

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