normality

• Normality


  Relationship between normality and molarity. Normality can only be calculated when dealing with reactions, because normality is a function of equivalents. Normality is the molarity of a solution multiplied by the number of moles of equivalents.
• Normality


  • Particularly useful in titrations calculations
• Percent by weight


  To make up a solution based on percentage by weight, one would simply determine what percentage was desired and the total quantity to be prepared.
• Percent by weight


  • 20% by weight aqueous solution of sodium chloride
• Making a 20% by weight aqueous solution of sodium chloride

  1. Determine 20% of 1 kg which is 200 g NaCl

  2. Add 800 g water to bring the total quantity to 1 kg
• Percent by volume


  Solutions based on percent by volume are calculated the same as for percent by weight, except that calculations are based on volume.
• Percent by volume

  • 20% by volume aqueous solution of sodium chloride
• Percentages are used more in the technological fields of chemistry (such as environmental technologies) than they are in pure chemistry
• Making dilutions


  The starting solution is referred to as the stock solution and the solution that you make is referred to as the working solution. It is easier to make and store smaller volumes of concentrated stock solution.
• Calculating dilutions


  1. Molarity and volume of the stock solution are inversely proportional

  2. MstockVstock = MworkingVworking
• Calculating dilutions


  • Start with a 12M concentrated solution of saline solution

  Experiment calls for 0.8 Liters of a 3.0M solution

  12M x Vol. Stock = 3.0M x 0.8L

  Vol. Stock = 3.0M x 0.8L / 12M = 0.2L