Question

Which type of reaction is `AlCl_3 + 3 KOH ->Al(OH)_3+ 3 KCl`?

Answer 1

A double replacement reaction

Explanation:

none of the atoms or polyatomic ions change the oxidations states, so it is not a oxidation reduction reaction.

The reaction follows the general form of a double replacement

`A^+B^- (+) C^+ D^-`= `A^+ D^- (+ ) C^+ B^-`
The positive three ion of Al disassociates with the Chlorine -1 ion.
then the still positive +3 ion of Al then combines with the -1 OH

The positive +1 K disassociates with the Hydroxide ion -1 ion then the still positive +1 K ion combines with the -1 Chlorine ion.

This is a classic example of a double replacement reaction.

Answer 2

This is a double replacement (double displacement) reaction.

Explanation:

In a double replacement reaction, the cations in two compounds switch places. The generic reaction is:

`color(red)"A"color(green)"X" + color(blue)"B"color(purple)"Y""` `rarr` `color(blue)"B"color(green)"X" + color(red)"A"color(purple)"Y"`,

where `color(red)"A"` and `color(blue)"B"` are the cations and `color(green)"X"` and `color(purple)"Y"` are the anions.

One of the products of a double replacement reaction must be water (neutralization), an insoluble gas (such as `"H"_2"` or `"CO"_2"`, or a precipitate (an insoluble solid).

`color(red)"Al"color(green)("Cl")_3("aq") + 3color(blue)"K"color(purple)("OH")("aq)"` `rarr` `"3"color(blue)("K")color(green)("Cl") + color(red)("Al")(color(purple)("OH"))"_3`

When the aqueous `"AlCl"_3"` and aqueous `"KOH"` solutions are mixed, an insoluble solid is produced. We can see that neither of the products is water or an insoluble gas, but one of the products is a precipitate because it is insoluble in aqueous solutions.

We can find out which product is the precipitate by consulting a solubility table like the one below. We can see that compounds containing alkali metal cations, such as `"K"^(+)"`, are soluble in aqueous solutions. We can also see that compounds that contain the hydroxide ion, `"OH"^(-)"`, are insoluble, and aluminum is not one of the exceptions. Therefore, the precipitate is the compound `"Al(OH)"_3"`.

The entire equation with physical states included is:

`"AlCl"_3("aq") + "3KOH(aq)"` `rarr` `"Al(OH)"_3("s") + "3KCl(aq)"`

We can use a down arrow to show that the solid is a precipitate.

`"AlCl"_3("aq") + "3KOH(aq)"` `rarr` `"Al(OH)"_3darr + "3KCl(aq)"`