1
$\begingroup$

Looking for random chemicals, I found a reference on the anion and thought that it could be synthesised from common laboratory reagents:

$$ \begin{align} \ce{2 Al + 2 NaOH + 2 H2O &-> 2 NaAlO2 + 3 H2}\\ \ce{NaAlO2 + 4 HCl &-> NaAlCl4 + 2 H2O} \end{align} $$

The first reaction obviously occurs at high yield at STP. Does the second reaction occur at STP or not? If not, how can the $\ce{AlCl4^-}$ ion be synthesised?

$\endgroup$
  • 1
    $\begingroup$ You do not synthesize ions, you synthesize compounds. $\endgroup$ – Nilay Ghosh Jan 1 at 6:05
1
$\begingroup$

Note that the first reaction would require substantial amount of heat to assure the designated product $\ce{NaAlO2}$ is formed (nowhere near STP):

$$\ce{2 Al(s) + 2 NaOH(l) + 2 H2O(g) ->[\pu{\approx 450 °C}] 2 NaAlO2(s) + 3 H2(g)}$$

In aqueous solution the product would be tetrahydroxoaluminate $\ce{[Al(OH)4]-}:$

$$\ce{2 Al(s) + 2 NaOH(aq, conc) + 6 H2O (l) ->[Δ] 2 Na[Al(OH)4](aq) + 3 H2(g)}$$

Synthetic procedure from "common laboratory reagents" is described in Brauer's Handbook of Preparative Inorganic Chemistry [1, p. 816]:

Sodium Tetrachloroaluminate

$\ce{NaAlCl4}$

$$\ce{\underset{58.4}{NaCl} + \underset{133.4}{AlCl3} = \underset{191.8}{NaAlCl4}}$$

The reaction is carried out in a Pyrex vessel (Fig. 245), which should be as compact as possible. The stoichiometric amounts of C.P. $\ce{NaCl}$ and freshly sublimed $\ce{AlCl3}$ are introduced into the pear-shaped part of the reaction vessel.

Apparatus for the preparation of sodium tetrachloroaluminate
Fig. 245. Preparation of sodium tetrachloroaluminate.

The filling is done under nitrogen and the vessel should be very clean and dry. A melting point capillary is then affixed underneath the ground joint; the apparatus is evacuated to a high vacuum and torch-sealed. It is then immersed as deeply as possible in an oil bath at 200–240 °C. The $\ce{AlCl3},$ which tends to sublime onto the cool parts of the wall, is driven back by passing a luminous flame over the condensate spots. When the flask contents have become a nearly clear melt, they are poured hot into the side flask of the vessel. The product solidifies on cooling.

References

  1. Handbook of Preparative Inorganic Chemistry, 2nd ed.; Brauer, G., Ed.; Academic Press: New York; London, 1963; Vol. 1.
| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.