stoichiometry

Balancing equations: a chemical equation is balanced when there are equal number of atoms and charges on both sides of the equation

State symbols:

• (s) = solid
  
• (l) = liquid
  
• (g) = gas
  
• (aq) = aqueous solution

1) Masses

• Relative atomic mass (Ar) is the average mass of naturally occurring atoms of an element on a scale where the C-12 atom has a mass of exactly 12 units.
• Relative molecular mass (Mr) is the sum of the relative atomic masses.

2) The Mole Concept

• A mole of a substance is the amount that contains the same number of units as the number of carbon atoms in 12 grams of carbon-12. 
• A mole is the Ar or Mr expressed in grams e.g. 1 mole of Carbon-12 is equal to 12 grams.
• It is equal to
  

\[6.02214076\times 10^{23}mol^{-1} atoms\]

• this number is called Avogadro’s constant.

Number of Moles:

\[Moles=\frac{Mass}{Molar Mass}\]

Moles in Gases:

\[Moles=\frac{Volume(dm^{3})}{24}\]

Concentration:

\[Concentration=\frac{no. of moles}{volume}\]

• Moles per dm3
  
• 1mol/dm3 = 1M
  
• Grams per dm3, g/dm3 

* 3) Calculate Empirical Formulae

* 4) Calculate Percentage Yield and Percentage Purity

\[Percentage\: yield=\frac{Actual\: \: amount\: of\: product}{Theoretical\: amount\: of\: product}\times 100\]