Question

Question #878a9

Answer 1

Manganese(II) chloride tetrahydrate.

Explanation:

You're dealing with a hydrate, which is a compound that consists of

• the anhydrous salt, which in this case is `"MnCl"_2`
• the water of crystallization, which in this case is `4"H"_2"O"`

The first thing to do here is to focus on the anhydrous salt. Notice that the salt contains chloride anions, which as you know carry a `1-` charge.

This implies that the charge on the manganese cation will be equal to `2+`, since you need two chloride anions to balance the total positive charge coming from the cation.

Because manganese is a transition metal, which implies that it can form cations of different charges, you must use a Roman numeral to name it.

In this case, the manganese cation carries a `2+` charge, so add the (II) Roman numeral to its name to get

`"Mn"^(2+) ->` the manganese(II) cation

The anhydrous salt will be called

`"MnCl"_2 ->` manganese(II) chloride

Now for the water of crystallization. Notice that each formula unit of this hydrate contains

• one formula unit of manganese(II) chloride, `1 xx "MnCl"_2`
• four molecules of water, `4 xx "H"_2"O"`

At this point, you must turn to a Greek prefix.


Since you have four water molecules per formula unit of hydrate, use the prefix tetra-.

The full name of the hydrate will thus be

`"MnCl"_2 * 4"H"_2"O" ->` manganese(II) chloride tetrahydrate