1.2: Amount Of Substance Flashcards
(15 cards)
What is the equation for %yield?
Actual / theoretical x100
What is the formula for atom economy?
Mr desired product / Mr total reactants x100
What is the ideal gas equation?
PV=nRT
Where ,
P= pressure (Pa)
V= volume (m3)
N= amount of a gas (moles)
R= gas constant (8.31 J/K)
T= temperature (K)- C+273
How could you check that all the water has been removed from a hydrous substance
Reheat to a constant mass
What conditions in the fermentation of glucose to ethanol can cause the production of ethanoic acid as a biproduct?
Aerobic conditions, air gets in causing oxidation.
What is ‘an appropriate number of significant figures’?
The minimum number of significant figures in the question
What are the two universal indications used in titrations?
What are their colour changes?
- phenolphthalein: alkali=pink, acid=colourless
- methyl orange: alkali=yellow, acid=colourless
Why are only a few drops of universal indicator used in titrations?
Too much, the indicators colour masks the colour/colour change were looking for
What must concordant results be within?
- 0.01cm^3
How do you calculate mean titre?
- mean of concordant results
What is the genral titration equation?
- acid + alkali —> salt + water
What is the biuret uncertainty and therefore the total uncertainty?
- +/- 0.05
- 0.1
What are the genral steps of a titration calculation
- write equation
- calculate moles of known solution
- molar ratio
- calculate moles unknown solution
- calculate mass with Mr
What are back titrations?
- excess of an acid or alkali is reacted with a substance of unknown mass of substance
- remove left over acid/alkali and titrate it with an alkali/acid
- find volume and therefore moles of acid in excess
- multiply moles up to volume(if changed, e.g only 25cm^3 of a 250cm^3 solution is titrated)
- use molar ratio to find moles of substance
- find mass
What are the general steps of a back titration?
- find moles of titration, use molar ratio to find moles of excess
- fix volume
- molar ratio with unknown substance
- find moles and mass