formulae and amounts (2) Flashcards
what is a mole
amount of chemical species found in 12g of carbon 12
what is Avogadros constant
the number of atoms in exactly 12g of carbon 12
(6.02 x 10^23 mol-1)
what is molar mass
mass of one mole of the substance expressed in gmol-1
what is empirical formula
smallest whole number ratio of atoms of each element in a compound
what is molecular formula
the actual number of atoms of each element in a compound
what is a spectator ion
ions that do not take part in the reaction
what does ‘hydrated’ mean
a compound that has molecules of water of crystallisation
what is a solution
solvent (dissolves solute)
what is a standard solution
the one with accurately known concentration
what is mass concentration
mass of solute per volume of solution
(gdm-3)
what is molar concentration
moles of solute per volume of solution (moldm-3)
what is primary standard
a substance used for preparation of a standard solution by weighing
what is Avogadros law
provided the conditions of temperature and pressure are the same, equal volume of gases contain the same number of molecules
what is molar volume
the volume of 1 mole of gas
what is a displacement reaction
more reactive element reacts to take the place of less reactive element in a compound
what is a precipitation reaction
one that produces an insoluble solid
what is an error
a discrepancy between the value obtained in the experiment and an actual value
what is precision
refers to how close to each other are the values obtained in an experiment
what is accuracy
refers to how close the values are to the actual value
what are concordant results
results that lie close to eachother
e.g titration +/- 0.10
what is a margin of error
the range in which the true value of a measurement could lie
e.g burettes +/- 0.05
what is a random error
they occur when conditions are varied in an unpredictable manner
what is a systematic error
errors which are constant when you repeat an experiment. they usually are a result of the apparatus used
what is the equation for percentage uncertainty
uncertainty/reading x100
what is the equation for percentage yield
actual yield/theoretical yield x100
equation for a mole of any substance
6.02x10^23 atoms/molecules
equation for number of particles
Avogadros number x number of moles
equation for moles
mass/Mr
equation for conc (2)
mass/vol
moles/vol
what do carbonates produce in acid base reaction
salt water and carbon dioxide
how to use molar gas vol to work out moles
mol= vol/molar gas vol
what is molar gas vol at standard temperature and pressure
22.4 (273K and 101.3KPa)
what is molar gas vol at room temp
24 (293K + 101KPa)
what is the ideal gas equation
pv= nRT
steps for making standard solution in titration
1) weigh amount of solid precisely using mass balance and plastic weighing boat
2) transfer solid from boat to a beaker, wash any solid left behind into beaker using deionised water
3) dissolve solid fully using deionised water and stir with glass rod
4) transfer solution to volumetric flask, using funnel to avoid spillage and rinse the beaker and glass rod into flask to make sure it has all transferred
5) fill to graduation line with deionised water, use pipette when it gets close to top
6) invert flask a few times with lid on to ensure it is thoroughly mixed
what colour is phenolphthalein indicator
colourless when acidic and pink when alkali
what colour is methyl orange indicator
yellow when acidic and red when alkali
what is equation for percentage error
uncertainty/reading x100
how can you reduce errors
using more precise equipment
using larger volume of liquid
what is atom economy equation
molecular mass of desired product/ molecular mass of all reactants x100
why do companys prefer a high atom economy
-raw materials used more efficiently, more sustainable
-produce less waste so benefits environment
-less by-products so less time and money spent seperating these from desired product
