unit 4 - how to pass: standard solutions and dilutions Flashcards
How can standard solutions be prepared?
By accurate dilution by pipetting an appropriate volume of a standard solution into a volumetric flask, making up to the graduation mark with solvent, stoppering and inverting.
What must a primary standard be?
Available in a high state of purity, be stable when solid and in solution, be soluble and have reasonably high GFM.
What do examples of primary standards include?
Sodium carbonate, hydrated oxalic acid, potassium hydrogen phthalate, silver nitrate, potassium iodate and potassium dichromate.
Why isn’t sodium hydroxide a primary standard?
It has relatively low GFM, is unstable as a solid (absorbs moisture) and unstable as a solution.
What must happen to sodium hydroxide solution before it can be used in volumetric analysis?
It must be standardised.
How do you calculate the dilution factor?
dilution factor = total volume after dilution / initial volume added
What happens when a concentrated solution is diluted?
The amount of solute does not change, only the amount of solvent.
