What incorrect information is given by the formula MgOH2 instead of the correct formula, Mg(OH)2 ?

i don't understand the question though.

Mg(OH)2 means we have 1 Mg, 2 O, and 2 H atoms.

MgOH2 means we have 1 Mg, 1 O and 2 H atoms.
The first formula is magnesium hydroxide. The second one doesn't exist.
So the incorrect information is that the wrong formula gives the wrong number of atoms and the wrong ratio of atoms to one another.

The incorrect information given by the formula MgOH2 is that it implies that the oxygen (O) is bonded directly with the hydrogen (H) without involving the magnesium (Mg) atom. However, the correct formula for magnesium hydroxide is Mg(OH)2, which represents the correct arrangement of atoms in the molecule.

To understand the correct formula, it is helpful to know the valency or charge of each element in the compound. Magnesium (Mg) has a charge of 2+, and hydroxide (OH-) has a charge of 1-. To balance the charges, two hydroxide ions are needed for every one magnesium ion, resulting in the formula Mg(OH)2.

In general, when parentheses are used in a chemical formula, it indicates that the elements within the parentheses are grouped together and are bonded as a unit. In this case, the hydroxide ion (OH-) is a polyatomic ion consisting of one oxygen atom bonded with one hydrogen atom, and this polyatomic ion is then bonded with the magnesium ion.

So, when writing chemical formulas, it is crucial to correctly represent the arrangement and bonding of atoms in a compound by using parentheses when necessary, as seen in Mg(OH)2 for magnesium hydroxide.

Is that not obvious?