physical chemistry...... mole concept......
basic formulae and tips.....
methods of calculations of mole:-

• if no of some spieces is given than no of moles= given no of spieces/N_a
•  if weight is given than no of moles = given weight/ molar weight
• the above formula can be used for compounds also...
• if volume of a gas is given along with its temperature T and pressure P, than use n=PV/RT where R = 0.0821 lit-atm/mol(when p is in atmosphere and V in litre)
• 1 mole of any gases at STP occupies 22.4 litres....
• Empirical formula is  simple ratio  formula  of  the  compound.
• molecular formula is the formula depictiong the actual no of atoms in one molecule of the compound....
• molecular formula= empirical formula * n
• n = molecular mass/ empirical formula mass