Stolchiometry
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Find the mole
mass / mr
percentage yield
[ Actual percentage/ theoretical percentage ] x 100
molecular formulae
Mass given / Mr from empirical formula
Empirical formula steps [5]
1) Mass (Pecentage but written as mass) 2) Mr 3) Mole 4) Ratio (all number divided by the smallest mole) 5) Write the formula using the ratio
Define mole
unit of amount of substance and that one mole contains 6.02 × 1023 particles (Avogadro constant
Avogadro constant
The number of particles in 24 dm3 of a gas at r.t.p.
What does avogadros number tell us 6.02 x 10^23
The number of atom/molecules of an element/compound
Limiting reactant
The reactant that gets used up first, the rest is excess reactant
Which one is in excess? Na = 0.4 mole S= 0.25 mol 2Na+S
To react completely 0.40 moles of Na requires 0.20 moles of S and since there are 0.25 moles of S, then S is in excess Na is therefore the limiting reactant
Calculate vol using rtp
Vol (dm3) = Mol x RTP24 (dm3 mol-1)
Why is it usually necessary to include a number in the name of the compounds of transition elements
A transition element has more than one oxidation state
Ammonium
NH4+
Hydroxide
OH-
Nitrate
NO3-
Sulfate
SO4 2-
carbonate
CO32-
Hydrogen carbonate
HCO3-
Ammonium
NH4+
Volume (dm3 or L)
(24dm3 or L) RTP x Mole
Concentration (Mol/dm3)
Mole / Volume (dm3)
Methyl orange change to what colour in acid
Red to yellow from black
Relative atomic mass
Average mass of the isotopes of an element compared to 1/12th of the mass of an atom of 12carbon