Diatomic Molecules and Essential Reactions

Unit 3

Diatomic Molecules

Molecules that can’t exist by themselves(They can in compounds). The ==seven== diatomic molecules are:

• Oxygen: O2
• Hydrogen: H2
• Nitrogen: N2
• Fluorine: F2
• Chlorine: Cl2
• Bromine: Br2
• Iodine: I2

  Whenever you make a species list remember to write the number of elements, not compounds.

Essential Reactions

Synthesis: 2 simple reactants produce ==ONE== product. a+b →c. Ex: 2Mg + O2→ 2MgO

Decomposition: ONE reactant breaks down into simpler products. ab→a+b. It always needed a catalyst it involves one complex compound breaking down into simpler ones. ==A catalyst is anything that starts a reaction or makes it go faster.==

Single Replacement: A more active element ==replaces== a less active ==similar== element in a compound. ^^Metals replace metals, and non-metals replace non-metals^^. Hydrogen can replace both. In water and acid, hydrogen is a metal, but in everything else, it’s a non-metal. Lithium is the most active metal and gold and silver are the least active ones. a+bx→ax+b. Ex: 2Mg+2HCl→ 2MgCl + H2.

Double Replacement: The cations of two ionic compounds switch compounds. ax+by→ay+bx.

Ex: 3CuCl2 + 2NaPo4 → 6NaCl + Cu(Po4)2

Combustion Reaction: A hydrocarbon burns in the presence of oxygen to produce Carbon Dioxide and Water. CxHy + O2 → CO2 + HOH. Ex: C3H8 + O2 → CO2 + 4HOH

Example of a Possible Word Problem:

Calcium Nitrate reacts with Lithium Sulfate to produce Lithium Nitrate and Calcium Sulfate:

-Ca(No2)2 + Li(So4) → 2LiN02 + CaSO4 (This is an example of double replacement.