Topic 2 - Quantitative Analysis Flashcards
Moles formula of solids
Moles = Mass/Mr
Moles formula of solutions
moles = concentration x volume
What is hard water?
Hard water contains Ca2+ andMg2+ ions because the water flows over rocks containing magnesium sulfate or calcium carbonate. It wont easily form a lather with soap and makes scum instead.
What is temporary hardness caused by
Calcium hydrogencarbonate (Ca(HCO3)2)
What is permanent hardness caused by
Dissolved calcium sulphate
How do you remove temporary hardness
Boil it and the calcium hydrogencarbonate decomposes to from insoluble CaCO3.
How do you remove permanent hardness
Ion exchange resin. Contains lots of sodium or hydrogen ions and ‘exchanges’ them for calcium or magnesium ions in the water.
Word equation for removing temporary hardness
Calcium hydrocarbonate -> calcium carbonate + water + carbon dioxide.
symbol equation for removing temporary hardness
Ca(HCO3)2 (aq) -> CaCO3 (s) + H2O (l) + CO2 (g)
Symbol equation for removing permanent hardness
Na2Resin(s) + Ca2 (aq) -> CaResin (s) + 2Na+ (aq)
What are titrations used for
to find concentration
what type of reaction is a titration
neutralisation
What is the ionic equation for a titration
H+ (aq) + OH- (aq) -> H2O(l)
*How do you do a titration
wash burette and fill with acid
use pipette to put 25cm of alkali into conical flask
add suitable indicator
add acid slowly to alkali, near end point drop by drop, until indicator changes colour
repeat until you get concordant results
*What indicators are used in titrations
Phenolphthalein Pink - clear
Methyl Orange yellow - red
How do you make a soluble salt using an acid and an insoluble reactant (base)
add base to acid, solid will dissolve.
Filter excess solid to get solution
Heat to slowly evaporate water and crystallize salt
How do you make a soluble salt using an acid and a soluble reactant
have to put exact amount in to neutralise, can’t put in too much and filter out whats left because reactants are soluble.
Do titration to find out how much alkali is needed to neutralise.
Then carry out experiment without indicator so it is not contaminated.
The solution that remains contains only salt and water so evaporate off the water and you will be left with a pure dry salt.
Equation of copper oxide and hydrochloric acid
CuO + 2HCl -> CuCl2 + H2O
equation of sulphuric acid and sodium hydroxide
H2SO4 + 2NaOH -> Na2SO4 + H2O
