AP Chemistry/Reactions

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  • Reactants form products.
  • Reactions may be exothermic (releasing heat) or endothermic (absorbing heat).

Types of Reactions[edit]

  • Synthesis: A + B → AB
  • Decomposition: AB → A + B
  • Single Replacement: AB + C → AC + B.
  • Double Replacement: AB + CD → AD + CB.
    • Precipitation - when two ionic compounds are dissolved in a solvent, they form four ions. Quite often, the positive ion from one compound will react with the negative ion from the other, forming an insoluble compound. This compound precipitates to the bottom as a solid.
    • Neutralization - when an acid and base are mixed, water and a salt will form.

Redox Reactions[edit]

These are reactions where the oxidation numbers of particles change. The particle whose oxidation number decreases is reduced, and is called an oxidizing agent. The other particle is oxidized, and is called a reducing agent. If oxygen is the oxidizing agent, the reaction is called combustion.

Predicting Chemical Reactions[edit]

Types of Reactions[edit]

There are several guidelines that can help you predict what kind of chemical reaction will occur between a mixture of chemicals.

However, not all elements will react with each other. To better predict a chemical reaction, knowledge of the reactivity series is needed.

Reactivity[edit]

  • Red: elements that react with water and acids to form hydrogen gas, and with
oxygen.
  • Orange: elements that react very slowly with water but strongly with acids.
  • Yellow: elements that react with acid to form hydrogen gas, and with oxygen.
  • Grey: elements that react with oxygen (tarnish).
  • White: elements that are often found pure; relatively nonreactive.

Most Reactive

Cs
K
Na
Li
Sr
Ca
Rb
Ba
Mg
Al
(C)
Mn
Zn
Cr
Fe
Cd
Co
Ni
Sn
Pb
(H2)
Sb
Bi
Cu
Hg
Ag
Pt
Au

Least Reactive

Kinetics[edit]

  • Rate constant - constant only for a specific reaction and temperature.
  • Order of a reaction - add up all the exponents of the molarities.