chemistry - 3e - volumetric analysis Flashcards

1
Q

What is a standard solution?

A

A solution of accurately known concentration.

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2
Q

How can standard solution be prepared?

A

 weighing a primary standard accurately
 dissolving in a small volume of solvent (usually deionised or
distilled water) in a beaker
 transferring the solution and rinsings into a volumetric flask
 making up to the graduation mark with solvent
 stoppering and inverting

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3
Q

What is another way of preparing standard solutions?

A

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.

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4
Q

What must a primary standard be?

A
  • be available in a high state of purity
  • be stable when solid and in solution
  • be soluble
  • have a reasonably high GFM
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5
Q

What are some examples of primary standards?

A
  • sodium carbonate
  • hydrated oxalic acid
  • potassium hydrogen phthalate
  • silver nitrate
  • potassium iodate
  • potassium dichromate
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6
Q

Why is sodium hydroxide not a primary standard?

A

As it has a relatively low
GFM, is unstable as a solid (absorbs moisture) and unstable as a solution.

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7
Q

What must happen to sodium hydroxide before being used in volumetric analysis?

A

It must be standardised.

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8
Q

What is EDTA?

A

An important complexometric reagent and can be used to determine the concentration of metal ions in solution.

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9
Q

What are back titrations used for?

A

To find the number of moles of a substance by reacting it with an excess volume of a reactant of known concentration.

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10
Q

In a back titration, what happens to the resulting mixture?

A

It is then titrated to work out
the number of moles of the reactant in excess.

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11
Q

When is a back titration useful?

A

When trying to work out the quantity of substance in a solid with a low solubility.

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