GENCHEM MIDTERMS

• Combination/Synthesis Reactions


  • Occurs when two or more reactants interact to form a single product. It is expressed in the general formula: A + B = AB
• Decomposition Reactions


  •Involve breaking of a large particles into smaller substance. This indicates that this type of reaction has a single reactants producing two or more products. The general formula is: AB --> A + B
• Single Replacement Reactions


  •In this reaction, a more active uncombined or free element reacts with a compound by displacing the less active metal or nonmetal ion in the substance. The general formula is: A + BC -->AC + B
• Double Replacement


  • In this reaction, the positive and the negative ions of the reactants involved exchanged partners. From this, we can deduce that this type of reaction involves two or more compounds as reactants producing also two compounds by exchanging ions. The general formula is: AB + CD → AD + CB
• Mole

  A mole is the amount of pure substance containing the same number of chemical units as there are atoms in exactly 12 grams of carbon-12 (i.e. 6.023 x 1023).
• Avogadro's Number

  is defined as the number of elementary particles (molecules, atoms, compounds, etc.) per mole of a substance. It is equal to 6.022×10 23 mol -1 and is expressed as the symbol NA.
• Avogadro’s number is sort of like a bridge. It bridges chemistry and atomic physics. In chemistry we measure things based on their bulk properties. Things like mass (total mass), pressure, volume, temperature. However, when we consider these things from an atomic perspective we look at individual atoms and the momentum, velocity of these particles. Avogadro’s number connects these two ideas and allows us to explore atomic-level things by measuring macroscopic level quantities. It’s a big deal.
• Mole

  Chemistry is a quantitative science - we need a "counting unit."