Chemistry solubility

• bonkysleuth

  6 Sep 09, 11:52

  Just a simple question,

  Is zinc hydroxide soluble in water? (if i'm not wrong, most soluble hydroxides belong to group 1 metals)

  If we heat NaOH, do we get Na2O and water?

  Thanks

• UltimaOnline

  6 Sep 09, 12:24

  Zn(OH)2 is an insoluble ppt, but can form a soluble complex ion of tetrahydroxozincate(II) ion, in excess OH-(aq). NaOH is stable (as Na+ has relatively low charge density), and will not lose water to form Na2O. When excess water is evaporated away, you will get white solid NaOH(s). On the other hand, Zn2+ has relatively higher charge density, is more unstable and hence Zn(OH)2 will lose water when heated to form ZnO(s). Zinc oxide is yellow when hot, white when cold; the yellow colour arises from interactions in the crystal lattice, and not due to d-d* transition, since Zn2+ has no partially filled d-orbitals and doesn't qualify as a transition metal.
• anpanman

  11 Sep 09, 19:34

  Hi fellow forumers!

  Quite an interesting question regarding the heating of NaOH. So, we still have NaOH (s) when we heat it? Strange.

• Garrick_3658

  12 Sep 09, 01:25

  Decomposition of heated compounds only occur for the more unstable carbonates, not the common hydroxides or oxides.

• yiha093

  13 Sep 09, 02:03

  erm... ok guys i believe miscommunication.. ts is taking O lvls right? : )