1. Synthesis Reactions1. Synthesis Reactions

• Occur when two or more reactants (usually Occur when two or more reactants (usually elements) join to form a compound.elements) join to form a compound.

General Formula:General Formula: A + B A + B AB AB

(where A and B represent elements)(where A and B represent elements)

Chapter 6: Chemical Reactions Chapter 6: Chemical Reactions Occur in Predictable Ways Occur in Predictable Ways

Ionic:Ionic:• Magnesium metal reacts with oxygenMagnesium metal reacts with oxygen

gas to form magnesium oxide.gas to form magnesium oxide.

• 2Mg + O2Mg + O22 2MgO2MgO

Covalent:Covalent:• Nitrogen gas and oxygen gas join to form dinitrogen Nitrogen gas and oxygen gas join to form dinitrogen

monoxide.monoxide.

• 2N2N22 + O + O22 2N2N22OO

……can produce ionic or covalent compoundscan produce ionic or covalent compounds

2. 2. DecompositionDecomposition

• are the opposite of synthesis reactionsare the opposite of synthesis reactions• A compound breaks down into two or more products A compound breaks down into two or more products

(often elements).(often elements).

General Formula:General Formula:

AB AB A + B A + B

(where A and B represent elements)(where A and B represent elements)

Ionic and Covalent Compounds can DecomposeIonic and Covalent Compounds can Decompose

Ionic:Ionic:• Table salt, sodium chloride, can be broken down into Table salt, sodium chloride, can be broken down into

sodium metal and chlorine gas by melting salt at 800ºC sodium metal and chlorine gas by melting salt at 800ºC and running electricity through it.and running electricity through it.

• 2NaCl2NaCl 2Na + Cl2Na + Cl22

Covalent Covalent • By running electricity through water, By running electricity through water,

the water molecules decompose into the water molecules decompose into hydrogen and oxygen gases.hydrogen and oxygen gases.

• 2H2H22OO 2H2H22 + O + O22

3. Single Replacement3. Single Replacement

• When one When one element from a compoundelement from a compound is is replaced with a replaced with a separate elementseparate element

• Two types, based on whether the single element Two types, based on whether the single element is a metal or a non-metalis a metal or a non-metal

General Forms:General Forms:• A + BC A + BC B + AC where A is a metal, or B + AC where A is a metal, or• A + BC A + BC C + BA where A is a non-metal C + BA where A is a non-metal

The Two Types:The Two Types:

• When A is a When A is a metalmetal::• Aluminum foil in a solution of copper II chloride Aluminum foil in a solution of copper II chloride

produces solid copper and aluminum chloride.produces solid copper and aluminum chloride.

• Al + CuClAl + CuCl22 Cu + AlCl Cu + AlCl33

• When A is a When A is a non-metalnon-metal::• When fluorine is bubbled through a sodium iodide When fluorine is bubbled through a sodium iodide

solution, iodine and sodium fluoride are produced.solution, iodine and sodium fluoride are produced.

• FF22 + NaI + NaI I I22 + NaF + NaF

4. Double Replacement4. Double Replacement

• elements swap places between two compounds elements swap places between two compounds to form two new compounds.to form two new compounds.

• Two ionic solutions react to form a Two ionic solutions react to form a precipitateprecipitate (solid) and another (solid) and another ionic solutionionic solution

• General Form:General Form:• AB + CD AB + CD AD + CB AD + CB

4. Double Replacement Example:4. Double Replacement Example:

• potassium chromate and silver nitrate react to form a potassium chromate and silver nitrate react to form a red precipitate, silver chromate, in a solution of red precipitate, silver chromate, in a solution of potassium nitrate.potassium nitrate.

• KK22CrOCrO4(aq)4(aq) + AgNO + AgNO3(aq)3(aq) AgAg22CrOCrO4(s)4(s) + KNO + KNO3(aq)3(aq)

Note: the K and Ag switch places in the compounds.

5. Neutralization (aka Acid-Base reactions)5. Neutralization (aka Acid-Base reactions)

• occur when an occur when an acidacid and a and a basebase react to form a react to form a saltsalt and and waterwater..• acids (start with H)acids (start with H)

• bases (end in OH, or begin with NHbases (end in OH, or begin with NH44))

General FormGeneral Form::• Acid + base Acid + base salt + water salt + water

• HX + MOH HX + MOH MX + H MX + H22O O

(where X and M are elements)(where X and M are elements)

5. Neutralization Examples:5. Neutralization Examples:

• Sulphuric acid is used to neutralize calcium hydroxideSulphuric acid is used to neutralize calcium hydroxide::

HH22SOSO44 + Ca(OH) + Ca(OH) 22 CaSOCaSO44 + 2H + 2H22OO

• Phosphoric acid helps to neutralize the compounds that Phosphoric acid helps to neutralize the compounds that cause rust, such as iron (II) hydroxide.cause rust, such as iron (II) hydroxide.

2H2H33POPO44 + 3Fe(OH) + 3Fe(OH)22 FeFe33(PO(PO44))22 + 6H + 6H22OO

6. C6. Combustionombustion

• occurs when a compound or element reacts occurs when a compound or element reacts with oxygenwith oxygen

• Always makes COAlways makes CO22 and H and H22O O (in grade 10 examples)(in grade 10 examples)

• Aka. hydrocarbon combustionAka. hydrocarbon combustion

General Form: General Form: CCXXHHYY + O + O22 CO CO22 + H + H22OO

6. Combustion Examples:6. Combustion Examples:

• Natural gas (methane) is burned in furnaces to Natural gas (methane) is burned in furnaces to heat homesheat homes

CHCH44 + O + O22 COCO22 + 2H + 2H22OO

• An acetylene torch is used to weld metals An acetylene torch is used to weld metals togethertogether

2C2C22HH22 + 5O + 5O22 4CO4CO22 + 2H + 2H22OO

• Carbohydrates like glucose combine with oxygen Carbohydrates like glucose combine with oxygen in our body to release energyin our body to release energy

CC66HH1212OO66 + 6O + 6O22 6CO6CO22 + 6H + 6H22OOTake the Section 6.1 Quiz