Question

How would you identify the missing coefficient in the balanced equation and classify the type of reaction?

`Mg(OH)_2 + H_2SO_4 -> MgSO_4 + H_2O`

Answer 1

`"Mg(OH)"_2 "(s)"+ "H"_2"SO"_4 "(aq)" -> "MgSO"_4 "(aq)"+ color(blue)(2)"H"_2"O(l)"`

Explanation:

In order for the reaction to be balanced, the number of atoms of each element must be equal on both sides of the reaction arrow. On the left side, we have

`"Mg": 1`
`"O": 2 + 4 = 6`
`"H": 2 + 2 = 4`
`"S": 1`

And on the right side,

`"Mg": 1`
`"O": 4 + 1 = 5`
`"H": 2`
`"S": 1`

You'll notice that the products side is short two hydrogens and one oxygen. Coincidentally, `"H"_2"O"` just so happens to have that exact element ratio. We need one more `"H"_2"O"` molecule on the products side to balance this equation, so its coefficient becomes

`1` (understood, not shown) + `color(red)(1) = color(blue)(2)`

The balanced chemical equation is thus

`"Mg(OH)"_2 "(s)"+ "H"_2"SO"_4 "(aq)" -> "MgSO"_4 "(aq)"+ color(blue)(2)"H"_2"O(l)"`

This type of reaction is a special kind of double-replacement reaction (or metathesis reaction) called a neutralization reaction, in which an acid and a base react in aqueous solution to form a salt and (usually liquid) water.

Answer 2

`Mg(OH)_2` + `H_2SO_4` => `MgSO_4` + `2H_2O`

Metathesis Reaction or, Double Replacement Reaction or, Acid Base Reaction or, Ion Exchange Reaction.

Explanation:

There are two primary classifications of reactions
1. Oxidation-Reduction Reactions
2. Metathesis Reactions

Oxidation-Reduction Reactions are characterized by a change in oxidation states of the elements in the reaction.

Metathesis Reactions are Ion Exchange Reactions of the form
AX + BY => AY + BX where A, B, X & Y are Ions in aqueous solution. For a Metathesis Ion Exchange Reaction to occur, a product is formed that leaves the reaction system as a solid precipitate, soluble weak acid or weak base or a gas decomposition product. The Metathesis Reactions reaction is characterized by NO CHANGE in oxidation states of elements in the reaction process.