2.2 amount of substance Flashcards
charge of Zn and Ag
Ag+
Zn 2+
water of crystallisation
water molecules that exist in crystal structures
for every mole of salt, you have a certain number of moles of water of crystallisation
written as: .xH2O
salts are ionic compounds which can be hydrated or anhydrous
what is the connection with the salts and water?
water is polar and is attracted to ions in a salt
δ- oxygen is attracted to positive ions
δ+ hydrogen is attracted to negative ions
experiment to work out value of crystallisation
1.heat hydrated salt to remove water of crystallisation leaving behind anhydrous salt
2. hydrated mass - anhydrous mass = mass of water
3. work out moles of anhydrous salt and water
4. divide both mole values by smallest mole value to work out ratio of (salt : water)
ionic equation of:
H2SO4 + 2KOH -> K2SO4 + 2H2O
(2H+) + (SO4 2-) + (2K+) + (2OH-) -> (2K+) + (SO4 2-) + (2H2O)
CANCEL ions that appear on both sides
2H+ + 2OH- -> 2H2O
*final ionic equation charges must balance
spectator ions
ions that do not get involved in reaction
Avagadro’s number
6.02 x 10^23
calc number of particles/molecules
no. of particles = Avg number x moles
calc number of moles (mass and Mr)
moles = mass/Mr
calc number of moles (conc and vol)
moles = conc (moldm-3) x vol (dm3)
ideal gas equation
pV = nRT
p - pressure (Pa)
V - volume (m3)
n - moles
R - gas constant (8.31 JK-1mol-1)
T - temperature (K)
standard conditions
298K
100 kPa
m -> dm -> cm
m2 -> dm2 -> cm2 (area)
m3 -> dm3 -> cm3 (volume)
x10 x10
x100 x100
x1000 x1000
empirical formula
the simplest whole number ratio of elements in a compounde
percentage yield
percentage yield = (actual yield/theoretical yield) x 100
