Quantitative Anaylsis Flashcards
What is a mole?
The mass of an element equal to is realities atomic number always contains 6x10^^23 atoms
How to calculate the number of moles?
Mass of element in grams/relative atomic mass
How to calculate the number of moles of a compound
Mass of compound in grams
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Relative Formula Mass
How to calculate concentration?
Number of moles of solute
Divided by
Volume of solution in dm3
How to make copper sulfate
Add insoluble copper oxide to sulfur if acid until no mor reacts.
Warm the mixture with a Bunsen burner.
Filter the unreacted solid copper sulfate crystals form by evaporating solution.
Filter off the crystals and leave do dry.
Describe how to carry out a titration
An indicator must be used. The acid is added and measured an amount at a time. The indicator changes colour when sufficient acid has been added. Use a burrette to measure the amount of acid added.
What happens when an acid dissolves in water?
It forms hydrogen ions
What happens when a solvable base is dissolved in water
It forms hydroxide ions
How to prepare in insoluble salt?
You can make soluble salts by reacting an acid with an insoluble base.
Add base to the acid, the solid will dissolve as the acid reacts. Excess solid will sink
Filter the excess solid to get a solution containing only salt and water
Heat it gently to evaporate the water and you are left with the salt
What instrument do you use to measure amounts
A pipette to add the alkali to a conical flask
Name two indicators used in titrations and their specific uses
Phenolphthalein is ed for weak acid and strong alkali
Methyl orange is used form strong acid and weak alkali
What colour is phenolphthalein in acids
It is colourless
How can you make a soluble salt
By reacting an acid and an insoluble reactant
Describe the method used to make a soluble salt
Add the insoluble base to the acid, the solid will dissolve in the acid. When this dissolving is finished the rest of the base will sink to the bottom. Filter out the excess solid to get the solution of dissolved salt and water. Finally gently hear it to evaporate off the water and crystallise the salt
Describe the method to make a soluble salt using acid and a sulfate reactant
Reacting an alkali or soluble base with an acid. You can’t tell when the reaction has finished as there is no sign the acid is neutralised. You need to carry out a titration to find the exact amount of alkali needed. Carry out the titration without indicator so not to contaminate it, evaporate off the water and you will be left with a pure dry salt
