PLEEEZE help

name the type of reaction

K + MgBr ->

Not enough information is provided. And not magnesium bromide is MgBr2. Is this a solution phase or exactly how is the K metal added to the MgBr2?

As DrBob has indicated, not all of the information has been provided. You probably meant:

2K(s) + MgBr2(aq) --> 2KBr(aq) + Mg(s)

There is a bit of the problem with this particular reaction in that potassium with react rather violently with water before it gets much opportunity to react with the magnesium bromide. Also metallic magnesium will react with water (see below) although not as rapidly as potassium.

Nevertheless, back to the reaction type there are the five types. Here is review. Which one do you think it is and why?

Synthesis (Formation) Reactions

General equation: A + B ---> AB

Elements and compounds combine to form larger more complicated reaction. There are fewer compounds on the product (right) side of the equation.

Examples:
2P + 5O2 → P2O5
3O2 → 2O3
2CoF2 + F2 → 2CoF3

Decomposition Reactions
General equation: AB ---> A + B

Compounds fall apart and form two or more products

Examples
Ca(ClO3)2 → CaCl2 + 3O2
2Au2O3 → 4Au + 3O2
C3H5(NO3)3 → CO2 + N2 + H2O + O2

Single Replacement (One element exchanges for another)