types of chemical reactions. states from this point forward, all components of a chemical reaction...
TRANSCRIPT
Types of Chemical Reactions
States
From this point forward, all components of a chemical reaction will need to show the state
There are 4 states
1. Solid
2. Liquid
3. Gaseous
4. Aqueous – Dissolved in water
An Aqueous substance will be ionic and is actually the ions separated from each other by water
Types of Chemical Reactions
There are only five (5) different types of chemical reactions: 1) Double Replacement
2) Single Replacement
3) Synthesis/Formation
4) Decomposition
5) Combustion
Reaction Type 1 – Double Replacement
Occur between two ionic compounds Does not happen with covalent compounds
Involves an exchange of cations (positive ions)
The cation of one compound trades places with the cation of another compound to form two new compounds
Double Replacement - Characteristics
occur in solution when the compounds are in an aqueous state (aq) reactants are either aqueous to begin with, or
solid compounds dissolved in water to form an aqueous solution of ions
in order to drive the reaction, one of the products must be removed from the aqueous solution
this can occur via one of three ways:
Double Replacement - Characteristics
1) Formation of a precipitate (an insoluble solid forms in the solution)
i.e.:
AgNO3 (aq) + NaCl (aq) NaNO3 (aq) + AgCl (s)
Solid silver chloride is formed as precipitate and comes out of the solution
Double Replacement - Characteristics
2) Formation of a gas
i.e.:
FeS (aq) + 2HCl (aq) H2S (g) + FeCl2 (aq)
Hydrogen sulfide gas is formed and comes out of the solution
Double Replacement - Characteristics
3) Water is formed when a hydrogen cation unites with a hydroxide anion
i.e.:
NaOH (aq) + HCl (aq) HOH (l) + NaCl (aq)
Water (HOH) is formed and comes out of the solution
Determining if a Double Replacement Reaction Occurs & Predicting the States of the Products
1) Formation of a Precipitate Use a “Solubility Table”
Look at the compounds formed, and use a solubility table to identify if a precipitate is formed
If a precipitate is formed, it will be written as a solid in the products
If no precipitate forms, the reaction will not occur. You will simply have a mixture of ions
Determining if a Double Replacement Reaction Occurs & Predicting the States of the Products
2) Formation of a gas
Solubility table is not helpful
More difficult to identify
Use your best judgment, or the info will be given in the question
3) Formation of water
If water is a product, it will be written as a “liquid”, not “aqueous” since it is a pure liquid
Yes, water is technically a covalent compound, however it is still present in double replacement reactions.
Sometimes it is helpful to write H2O as HOH symbolizing the joining of a H+ cation and an OH- anion
Identifying a Double Replacement Reaction
Double replacement reactions always have two ionic compounds on the REACTANTS side AND on the PRODUCTS side of an equation
*Two compounds react to form two new compounds* AB + CD CB + AD
A & C are cations, B & D are anions
A & C switch places
Reaction Type # 2 – Single Replacement
Single Replacement Reactions: Characteristics:
Atom (s) of a lone element replace the atom (s) of an element in a compound Metals replace metals (or cations replace cations)
Non-metals replace non-metals (or anions replace anions)
Single Replacement Reactions: Characteristics:
Metal Cation Replacement: For the reaction:
A + BC B + AC
A and B are cations A “replaces” B in the compound
Single Replacement Reactions: Characteristics:
Non-metal Anion Replacement: For the reaction:
D + EF ED + F
D & F are anions D “replaces” F in the compound Non metal replacements usually involve
halogens
Single Replacement Reactions
Restrictions on Single Replacement Reactions
Activity Series: A characteristic of metals and halogens
referring to their reactivity Determines whether or not a single
replacement reaction will occur or not Metals: on page 155 (table 7-2) there is
an activity series of metals arranged in order of decreasing activity
Non-metals (Halogens) : as you move down the group on the periodic table activity decreases
Restrictions on Single Replacement Reactions
A single replacement reaction WILL NOT OCCUR if the reactivity of the pure element reactant is less than that of the compound reactant i.e.:
Sn (s) + NaNO3 (aq)
no reaction b/c tin is less reactive than sodium
Restrictions on Single Replacement Reactions
A single replacement reaction WILL OCCUR if the reactivity of the pure element reactant is greater than that of the compound reactant i.e.:
Zn (s) + H2SO4 (aq) ZnSO4 (aq) + H2 (g)
Reaction occurs because the reactivity of zinc is higher than hydrogen
Identifying Single Replacement Reactions
Single replacement reactions ALWAYS have 1 lone element and 1 compound on the reactants side and the products side
Reactants will always be: 1 lone element + 1 compound
Products will always be: 1 lone element + 1 compound