Unit 3: Balancing Chemical Equations Section 3: Types of Chemical Reactions

Types of Chemical Reactions Synthesis Decomposition Single-displacement (single-replacement) Double-displacement (double-replacement) Combustion

Synthesis Two substances combine to form a compound – A + X  AX “2 things become 1” Ex: 2 Mg + O 2  2 MgO

Decomposition One compound breaks down into two different substances – AX  A + X “1 thing breaks down into 2” Ex: 2 NaCl  2 Na + Cl 2

Single-Displacement An element replaces a similarly charged element in a compound – A + BX  AX + B Ex: 2 Na + MgCl 2  Mg + 2 NaCl “positive replaces positive” – Y + BX  BY + X Ex: Cl KBr  Br KCl “negative replaces negative”

Double-Displacement Two original compounds form two new compounds – AX + BY  AY + BX Ex: FeS + 2 HCl  FeCl 2 + H 2 S

Combustion A substance that combines with oxygen to form carbon dioxide and water – __?__ + O 2  CO 2 + H 2 O Ex: C 6 H 12 O 6 + O 2  CO 2 + H 2 O

Practice Problems 1.N 2 + 3H 2  2NH 3 2.2KClO 3  2KCl + 3O 2 3.2H 2 + O 2  2H 2 O 4.C 3 H 8 + 5O 2  3CO 2 + 4H 2 O 5.FeCl 3 + 3NaOH  Fe(OH) 3 + 3NaCl 6.2K + MgBr 2  2KBr + Mg 7.2AgNO 3 + MgCl 2  2AgCl + Mg(NO 3 ) 2