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Zn + NaOH = Na2ZnO2 + H2??

  1. Oct 12, 2017 #1
    what just happened? if i did this in water could i do something like Zn + H2O > Zn2+ + 2OH- + H2 so you get ZnOH2 which gets another 2 OH added from NaOH to give Na2Zn(OH)4 nowwww.... somehow this is dehydrated twice.. how? why? why is this less stable than the oxide?
     
  2. jcsd
  3. Oct 12, 2017 #2

    Borek

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    Staff: Mentor

    Formulas of zincates and aluminates (and some other similar salts) are not well defined and depend on whether we talk about the solution or dried out salt (and how well dried out).
     
  4. Oct 12, 2017 #3
    ah so we're alright with the hydroxide? it's not .H2O though which is what id think when we talk about drying.

    also : how does Be(OH)2 react with HCl +H2O, it gives Be(OH)4Cl and no hydrogen gas. I'm having trouble understanding what's going on here
     
  5. Oct 15, 2017 #4
    If hydrogen is deoxidized (from oxidation state +1 to ±0) something else must be oxidized. In case of your first example it is Zn (from ±0 to +2) but Be(OH)2 is no reducting agent.
     
  6. Oct 15, 2017 #5

    jim mcnamara

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    You may also see the so-called water of hydration or water of crystallization - what borek mentioned above. When salts crystallize they may retain "extra" water inside the crystal. When I learned this many years ago, water of hydration was defined as water found inside the crystalline framework of a metal salt, which is not directly bonded to the metal cation. You will see it written like this ##ZnCl_2 \cdot 4H_2O##

    Edit: see - https://en.wikipedia.org/wiki/Water_of_crystallization
     
  7. Oct 16, 2017 #6
    but in BeOH4Cl Be has oxidation number as +5?
     
  8. Oct 16, 2017 #7

    Borek

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    No, Be has no +5 ON, never. Even fully ionized it can be +4 at most (compare its atomic number).

    Be(OH)2 reacting with hydrochloric acid behaves like a simple hydroxide.

    When reacting with alkalies it can produce beryllates, similar (when it comes to problems with the formula) to zincates and alluminates mentioned earlier. Other than that there is nothing unusual with these compounds, Be is always +2 in them.
     
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