Final Exam Review for Chemistry

Chem Final Exam
Combination
Combination reactions, also known as synthesis reactions, involve the combination of two or more substances into a single new substance:
A + B ---> AB
Many metal oxides, for example, absorb carbon dioxide (CO2) from the air to form carbonates:
CaO(s) + CO2(g) ---> CaCO3(s)
Decomposition
Decomposition reactions represent the reverse of the combination process in that one substance breaks down into two or more substances:
AB ---> A + B
Water, or H2O, for example, decomposes into its constituent elements when subjected to an electric current:
2 H2O(l) ---> 2 H2(g) + O2(g)

Single-Replacement
Single-replacement reactions occur when an element replaces one of the elements in a compound:
A + BX ---> AX + B where X represents the atom being exchanged.
Many metals, for example, react with acids to produce hydrogen and a metal salt:
Zn(s) + 2 HCl(aq) ---> ZnCl2(aq) + H2(g)
Double-Replacement
Double-replacement reactions involve two compounds exchanging elements:
AB + CD ---> AD + CB
Double-replacement reactions commonly occur when one of the products is not soluble and precipitates out of the reaction solution as a solid:
CaCl2(aq) + Na2CO3(aq) ---> CaCO3(s) + 2 NaCl(aq)
Combustion
Combustion reactions occur when substances, particularly those containing carbon, burn in the presence of oxygen to produce carbon dioxide and water:
CxHy + O2 ---> CO2(g) + H2O(g)
Methane, for example, with chemical formula CH4 combusts as:
CH4(g) + O2(g) ---> CO2(g) + 2 H2O(g)

Net Ionic Equations
Net ionic equations are equations that show only the soluble, strong electrolytes reacting (these are represented as ions) and omit the spectator ions, which go through the reaction unchanged. When you encounter net ionic equations on the test, you’ll need to remember the following solubility rules, so memorize them! Also keep in mind that net ionic equations, which are the bare bones of the chemical reaction, usually take place in aqueous