Types+of+Chemical+Reactions+-+First+4+Types

There are **five major types** of chemical reactions we learned, and I will introduce the **first four types** to you! type 1:Synthesis(or called Combination)

Combination and Synthesis means substances(two or more) react and form one more complex substance, and it is represented by the equation:

A+B+(others)→AB(A, B and others can be a compound or an element, and AB must be a compound )

examples: Cu(s) + O 2(g) →CuO(s)

2K(s) + Cl2(9)→ 2KCl(s)
CO2(g)+H2O(l)→H2CO3(aq)

Easy way to recognize: there will be only one product, and it is must be compound

How to predict product of the reaction: lt each element in its ionic state

example: H2(g)+2Cl2(g)→2HCl(g) （H is +1, and Cl is -1）

there are some practices here: http://www.files.chem.vt.edu/RVGS/ACT/notes/Practice_Predicting.html

type 2:Decomposition (image from [] ) Decomposition reaction means to break one molecule into two or more simple substances, and it is represented by the equation:

AB→A+B+(others) (AB must be a compound,and A, B and others can be a compound or an element)

examples: H2CO3(aq)→H2O(l)+CO2(g)

Easy way to recognize: there will be a single reactant in the reaction, and it must be a comound

How to predict product of the reaction: the original compound breaks into the elements which make it up

example: 2HgO(s)→Hg(l)+O2(g) (Hg and O2 can make up HgO)

type 3:Single Replacement

(image from http://en.wikipedia.org/wiki/Single_displacement_reaction)

Single replacement means a single free element replaces another element in a compound. RULE:the free element must be more reactive than the replaced one

AB+C→AC+B(C and B are metal) AB+C→CB+A(C and A are non-metal)

example: 2FeI2+Pb→PbI4+2Fe (metal replaces metal) FeI2+Cl2→FeCl2+I2（non-metal replaces non-metal）

easy way to recognize: the reactants always have a metal/non-metal element and a compund with another type of metal/non-metal, and the products should have been replaced already.

How to predict product of the reaction: metal replaces metal or the non-metal replaces non-metal

type 4:Double Replacement(or called Metathesis)

Double replacement means exchanging the partners of the compounds,and posiitive ions are always with negative ions

AB+CD→AC+DB

example: HCl(aq)+ NaOH(aq)→NaCl(s)+H2O(l) CaCO3(aq)+2HCl(aq)→CaCl2(s)+H2CO3(aq)

easy way to recognize: Two compounds and both of them exchange their partner,positive and negative ions are put together.

How to predict product of the reaction: the positive charge switch another positve charge,so it can be with another negative ion.

There is another special type of double replacement called neutralization.

NEUTRALIZATION is a reaction that involves the reaction of **acid** and **base,** the products are water and salt.

vocabulary:
acid: a chemical formula starting with H, and the charge of H is +1. examples:HCl,H2SO4 are acid(they both have +1 H)

base: a chemical formula ending with OH, and the charge of OH is -1. exampels: NaOH,Ba(OH)2 are base(they both have -1 OH)

salt: an ionic compound that is neither an acid nor a base. examples:NaCI, K2SO4 are salt(they are ionic coumpound and they are neither a base nor an acid)

Easy way to recogize: An acid reacts with a base produce water and salt.

How to predict product of the reaction: the products of the neutralization equation always include water, and another product is salt.