Question

Is the conversion of sodium perrhenate to the tetrabutylammonium salt a double replacement reaction?

Answer 1

Yes, the conversion of sodium perrhenate to a tetrabutylammonium salt is a double replacement reaction; this reaction is actually a salt metathesis reaction, which is an alternative name given to a reaction in which counterions (cations and anions) exchange partners.

The general form for a metathesis reaction looks like this

`"AX" + "BY" -> "AY" + "BX"`, where

`A`, `B` - cations;
`X`, `Y` - anions.

In your case, the reaction between sodium perrhenate, or `NaReO_4`, and tetrabutylammonium chloride, or `(CH_3(CH_2)_3)_4NCl` (you'll sometimes see this written as `N(C_4H_9)_4Cl`), will produce sodium chloride, or `NaCl`, and tetrabutylammonium perrhenate, or `N(C_4H_9)_4ReO_4`.

`NaReO_4 + N(C_4H_9)_4Cl -> NaCl + N(C_4H_9)_4ReO_4`

The reaction takes place in aqueous solution (aq), and the tetrabutylammonium perrhenate salt will precipitate from solution.

The counterions that will exchange partners are `Na^(+)` and `N(C_4H_9)_4^(+)` (cations), and `ReO_4^(-)` and `Cl^(-)` (anions).