Amount Of Substance Flashcards
How to work out number of particles
Moles x avogadros
How to find moles with mass and mr
Moles=mass/mr
How to work out moles with concentration and volume
Moles = concentration (moles dm-3) x volume(dm3)
What is the ideal gas equation and units
pV= nRT
pressure= Pa
Volume= metres cubed
Moles
R = gas constant
Temp = K
How to work out empirical formular
- mass/mr to find the moles
- divide by smallest number
How to work out molecular formula
- Calculate the relative mass of an empirical formula
- Divide relative formula mass by relative empirical mass
- multiply
charge of metals
positive
charge of non metals
negative
how to convert c to kelvin
add 273
charge of ammonium
NH4 +
charge of Hydroxide
OH-
charge of Nitrate
NO3 -
charge of Sulfate
SO4 2–
charge of Carbonate
CO3 2–
charge of Hydrogen carbonate
HCO3 –
charge is Phosphate
PO4 3 –
The water of crystallisation in calcium sulfate crystals can be
removed as water vapour by heating as shown in the following
equation.
CaSO4.xH2O(s) → CaSO4(s) + xH2O(g)
What is the method?
*Weigh an empty clean dry crucible and lid.
*Add 2g of hydrated calcium sulfate to the crucible and weigh again
*Heat strongly with a Bunsen for a couple of minutes
*Allow to cool
*Weigh the crucible and contents again
*Heat the crucible again and reweigh until you reach a constant mass (do this to ensure the reaction is complete).
Why shouldn’t large amounts of hydrated calcium sulfate, such as 50g, should not be used in this experiment of water of crystallisation
the decomposition is
likely to be incomplete.
Why does the crucible needs to be dry when doing the water of crystallisation
a wet crucible would give an inaccurate result. It would cause mass loss to be too large as the water would be lost when heating.
Why do we use a lid when experimenting water of crystallisation
The lid improves the accuracy of the
experiment as it prevents loss of solid from the crucible but should be loose fitting to allow gas to escape
atom economy formula
molecular mass of desired product/sum of molecular mass of all reactants x100
what does percentage yield tell us
how wasteful a process is
