CHEM REACTIONS

• two or more simple substances combine to create a more complex substance


  synthesis or combination
• a more complex substance is broken down into simpler substances


  decomposition
• a less reactive element is displaced by a more reactive element


  single replacement
• the cations of two compounds switch anions to form new products

  double displacement
• recognizable by the reaction of oxygen

  combustion reaction
• occurs when an acid reacts with a base


  acid-base reactions
• also known as neutralization reaction

  acid-base reaction
• also called redox reaction


  oxidation-reduction
• electrons move from one reactant to another

  oxidation-reduction
• loss of electrons

  oxidation
• gain of electrons

  reduction
• the species causing the loss of an electron

  oxidizing agent
• the species causing the gain of an electron

  reducing agent
• the ability of an atom to lose or gain an electron


  oxidation number
• two soluble ionic compounds react to form an insoluble product or precipitate


  precipitation reaction
• an insoluble solid that separates from the solution


  precipitate
• the area of study in chemistry that involves the examination of quantities of substances consumed and produced during chemical reactions


  stoichiometry
• unit of measurement; amount of substance that carries as many elementary entities as there are atoms in 12g of Carbon-12 isotope


  mole
• elementary entities are atoms, molecules, and other similar particles
• number of particles in a mole of a substance

  avogadro's number
• avogadro's number is equal to 6.022 x 10^23
• molar mass is defined as the mass of 1 mole unit of a substance
• Molecular formula shows the exact number of atoms of an element in the smallest unit of a substance
• Empirical formula tells which elements are present and the simplest whole-number ratio of their atoms
• Structural formula shows the location of the atoms relative to one another in a molecule and the number of chemical bonds between the atoms
• in free elements, each atom has an oxidation number of zero
• for monoatomic ions, the O.N. is equal to the charge of the ion
• all alkali metals have an O.N. of +1
• all alkaline earth metals have an O.N. of +2
• aluminum has an O.N. of +3
• the O.N. of oxygen in most compounds is -2, but in hydrogen peroxide (H202) and peroxife (o2^-2), it is -1
• the O.N. of hydrogen is +1, except when it is bonded to metals in binary compounds. in those cases, its O.N. is -1
• fluorine has an O.N. of -1
• other halogens (Cl, Br, and I) have negative O.N. when they occur as halide ions; when combined with oxygen, they have a positive O.N.
• in a neutral molecule, the sum of O.N. of all the atoms must be zero
• in a polyatomic ion, the sum of O.N. of all the elements in the ion must be equal to the net charge o the ion
• O.N. do not have to be integers
• energy is absorbed during reactions; cannot occur spontaneously; work must be done in order to achieve reaction


  endothermic reaction
• when absorbing energy, temperature drop is measured during reaction

  endothermic reaction
• characterized by positive heat flow

  endothermic reaction