Sodium Hydroxide Production and Reactions

Flashcards covering the advantages, disadvantages, and various chemical reactions involved in the Castner Kellner process and the use of Sodium Hydroxide.

Castner Kellner process

The industrial process used for the manufacturing of sodium hydroxide ($NaOH$).

Advantages of Castner Kellner process

The process is very efficient, gives products of high purity, and avoids the possible reaction between sodium hydroxide and chlorine ($Cl_2$) gas through the formation of separate chambers or the Diaphram process.

Disadvantages of Castner Kellner process

The process consumes a large quantity of electricity and involves vapours of Mercury that can leave the industry with waste water and contaminate the food chain despite strict control.

Reaction of $NaOH$ with $HCl$

$$NaOH + HCl \rightarrow NaCl + H_2O$$

Reaction of $NaOH$ with Ferric chloride ($FeCl_3$)

$$3NaOH + FeCl_3 \rightarrow 3NaCl + Fe(OH)_3(s)$$

Reaction of $NaOH$ with zinc chloride ($ZnCl_2$)

$$2NaOH + ZnCl_2 \rightarrow 2NaCl + Zn(OH)_2$$

Amphoteric nature of $Zn(OH)_2$

The $Zn(OH)_2$ precipitate is amphoteric and re-dissolves in excess of $NaOH$ to form a complex: $Zn(OH)_2 + 2NaOH \rightarrow Na_2ZnO_2 + 2H_2O$

Reaction of $NaOH$ with Ammonium chloride ($NH_4Cl$)

$NaOH + NH_4Cl \rightarrow NH_4OH + NaCl$, where the ammonium hydroxide further decomposes: $NH_4OH \rightarrow NH_3 + H_2O$

Reaction of $NaOH$ with Zinc ($Zn$) metal

$$2NaOH + Zn \rightarrow Na_2ZnO_2 + H_2$$

Reaction of $NaOH$ with Aluminum ($Al$) metal

$$2NaOH + 2Al + 2H_2O \rightarrow 2NaAlO_2 + 3H_2$$

Reaction of $NaOH$ with chlorine ($Cl_2$)

$$6NaOH + 3Cl_2 \rightarrow NaClO_3 + 5NaCl + 3H_2O$$