3-Quantitative Chemistry

• Law of conservation of mass


  No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants
• Chemical reactions involve Reactants and Products
• In a chemical reaction, the starting materials are called the reactants, and the chemicals that are formed are called the products
• Reactants


  The starting materials in a chemical reaction
• Products


  The chemicals that are formed in a chemical reaction
• The mass of the products equals the mass of the reactants in a chemical reaction
• Metal ions


  • Na+
  • Mg2+
  • Al3+
• Metal ions

  • Charge is often the same as the group number in the periodic table
• Transition metals can form several different ions
• Transition metal ions


  • Fe2+
  • Fe3+
  • Cu1+
  • Cu2+
• Non-metal ion charge


  Often related to group number in periodic table
• Some non-metal ions consist of several non-metal atoms
• Hydrogen ion H+ and ammonium ion NH4+ are positive non-metal ions
• Ionic compound


  Compound where the charges on the ions have to cancel out to leave an overall charge of zero
• Determining the formula of an ionic compound


  1. Identify the charges on the ions

  2. Ensure the charges cancel out to leave an overall charge of zero

  3. Write the formula
• Ionic compounds


  • Sodium chloride (NaCl)
  • Sodium oxide (Na2O)
  • Magnesium iodide (MgI2)
  • Lithium carbonate (Li2CO3)
  • Calcium hydroxide (Ca(OH)2)
  • Magnesium nitrate (Mg(NO3)2)
• Brackets are used when the subscript applies to the whole formula unit, not just the atom immediately before it
• Actual yield


  The amount of product actually produced by a reaction
• Atom economy


  The measure of the amount of starting materials that end up as useful products
• Avogadro constant


  The number of atoms, molecules or ions in a mole of a given substance
• Avogadro's law


  Equal amounts in moles of gases occupy the same volume under the same conditions of temperature and pressure
• Concentration


  The amount of substance (e.g. the mass) in a certain volume of a solution
• Conservation of mass


  The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants
• Limiting reactant


  The reactant that is completely used up since it limits the amount of products formed
• Mole


  Chemical amounts are measured in moles. The mole is the unit for amount of substance. The symbol for the unit mole is mol
• Percentage by mass


  A value representing the concentration of an element in a compound or a component in a mixture. It is calculated by the mass of a component divided by the total mass of the mixture, multiplied by 100
• Percentage yield


  The percentage ratio of the actual yield of product from a reaction compared with the theoretical yield
• Relative formula mass


  The sum of the relative atomic masses of the atoms in the numbers shown in the formula. It is numerically equal to the mass of one mole of a substance in grams
• Theoretical yield


  The maximum amount of product that could be produced from the given reactants, assuming a complete reaction takes place
• Thermal decomposition


  The reaction that occurs when heat is applied to a compound causing it to break down into its different chemical constituents
• Uncertainty


  All measurements have a degree of uncertainty regardless of precision and accuracy. Uncertainty can be due to the limitations of the measuring equipment or due to the skill of the experimenter carrying out the measurements
• A chemical formula shows the formula of a compound, with capital letters representing elements and small numbers representing the number of atoms of each element
• You are never allowed to change the small numbers in a chemical formula as this produces a different molecule
• Large numbers in front of a chemical formula represent multiple molecules of that compound
• Balancing a chemical equation

  1. Count the number of atoms of each element on the left and right sides

  2. Ensure the number of atoms of each element is the same on both sides

  3. Use large numbers in front of compounds to balance the equation
• Balancing the unbalanced equation

  1. Count the atoms on each side

  2. Add a large number in front of the compound on the right side to balance the iodine atoms

  3. Add a large number in front of the compound on the left side to balance the sodium atoms