Types of reactions and reactivity

1. Describe the trends found in the periodic table with respect to:

a) atom size

b) ionization energy

c) Electronegativity

•In a composition reaction, also known as a synthesis reaction, two or more reactants combine to form a single product.

•This type of reaction is represented by the following general equation. A + X --> AX

•Formation of binary compound from its elements2 Mg(s) + O2(g) --> 2 MgO(s)S8 (s) + 8 O2(g) --> 8 SO2(g)2 Na(s) + Cl2(g) --> 2 NaCl(s)

•Reactants can also be compounds.

CaO(s) + H2O(l) --> Ca(OH)2(s)

SO2(g) + H2O(l) --> H2SO3(aq)

CaO(s) + SO2(g) --> CaSO3(s)

In a decomposition reaction, a single reactant undergoes a reaction that produces two or more simpler substances.

Decomposition reactions are the opposite of composition reactions.

They are represented by the following general equation.

AX --> A + XDecomposition reactions take place only when energy is added.

a)Decomposition of Binary Compounds* compound breaks up into its elements

2 H2O (l) --> 2 H2 (g) + O2 (g)2 HgO (s) --> 2 Hg (l) + O2 (g)

b)Decomposition of Metal Carbonates* when heated, metal carbonates decompose into a

metal oxide and carbon dioxide

CuCO3 (s) --> CuO (s) + CO2 (g)

c) Decomposition of Metal Chlorates* when heated, metal chlorates

decompose into a metal chloride and oxygen

2 KClO3 (s) --> 2 KCl (s) + 3O2 (g)

*The equation represents an incomplete chemical reaction.

Al + Cl2 --> What is the product of the chemical reaction?

A.Al2Cl3

B.AlClC.AlCl2

D.AlCl3

*The chemical equation represents the reaction between sodium (Na) and oxygen (O2).

4 Na + O2 --> What is the product of this reaction?

A.2 Na2OB.2 NaOC.2 NaO2

D.2 Na2O2

•In a single replacement reaction, one element replaces a “similar” element in a compound.•Single replacement reactions can be represented by the following general equation: Element + Compound --> Element + CompoundA + BC --> B + AC •“Similar” = metals replace metals = nonmetals replace nonmetalsException: Hydrogen replaces metals and

metals can replace hydrogen

•Activity series is a list of elements organized according to the ease with which the elements undergo certain chemical reactions. •For metals, greater activity means a greater ease of lose of electrons (forming cations).•For nonmetals, it means a greater ease of gaining electrons (making anions).•Use the provided list to determine if any given SDR will occur.

 Metals Name Symbol Lithium Li+ Sodium Na+

Potassium K+ Rubidium Rb+ Barium Ba+2 Strontium Sr+2

Calcium Ca+2

 Decreasing activity

↓   

reacts with water and acids

Magnesium Mg+2

Aluminum Al+3

Manganese Mn Zinc Zn+2

Chromium Cr+3 Iron Fe Cadmium Cd+2 Cobalt Co+2 Nickel Ni+2

Tin Sn Lead Pb 

  

reacts with acids replacing hydrogen

Hydrogen H2 

 

Antimony Sb Bismuth Bi Copper Cu Mercury Hg Silver Ag+1

Platinum Pt Gold Au

   

fairly unreactive

•Examples:1. Cu(s) + AgNO3(aq) -->

2. Cl2(g) + NaBr(aq) -->

3. Mg(s) + HCl(aq) -->

•In double-replacement reactions, the positive ions of two compounds exchange places to form two new compounds.•Double replacement reactions can be represented by the following general equation:

AX + BY --> AY + BX

•Examples:1. KI (aq) + Pb(NO3)2 (aq) -->

2. Mg(C2H3O2)2 (aq) + Na3PO4 (aq) -->

• In a combustion reaction, a substance combines with oxygen (O2), releasing a large amount of energy in the form of light and heat.

•Most combustion reactions involve the reaction of a carbon-based compound with oxygen. The products are carbon dioxide and water.

•They are represented by the following general equation.X + O2 --> CO2 + H2O

•Examples:1. CH4 + O2 -->

2. C8H18 + O2 -->

3. C6H12O6 + O2 -->

*You have one minute to answer these two questions concerning today’s lesson.

*What was the most important thing you learned?

*What is one question you would still like answered?