1. Reaction Types Chapter 5.2

2. PATTERNS • There are millions of unique substances and millions of possible reactions. • However, there are only a few general types of reactions. • Think of them as patterns for reactions. • Here are four such patterns.

3. 1. Synthesis Reactions • A reaction where you take at least 2 substances and make a new, more complex compound. A + B  AB 2 Na + Cl2 2 NaCl 6 CO2 + 6 H2O  C6H12O6 + 6 O2

4. 2. Decomposition Reactions • A reaction where one compound breaks into at least 2 smaller compounds. AB  A + B 2 H2O  2 H2 + O2 C6H12O6 + 6 O2 6 CO2 + 6 H2O

5. 3. Combustion Reactions • A reaction where a compound and oxygen burn. A + O2 CO2 + H2O 2 CH4 + 4 O2  2 CO2 + 4 H2O 2 CH4 + 3 O2  2 CO + 4 H2O 2 CH4 + 2 O2  2 C + 4 H2O

6. 4. Displacement Reactions • A reaction where the atoms of one element take the place of another element in a compound. Single: XA + B  A + BX 3 CuCl2 + 2 Al  3 Cu + 2 AlCl3 Double: AX + BY  AY + BX Pb(NO3)2 + K2CrO4  PbCrO4 + 2 KNO3

7. RADICALS • Sometimes pieces of molecules “break” off. • These fragments have an available electron for bonding. • They react very quickly and easily with just about anything. • Sometimes this is okay • like in making plastics • Sometimes they are harmful • free radicals – why we take antioxidants