1. S e c t i o n t h r e e
B y :
Y o u s s e f B e r b a r
2.
3. Mole : 6.022 x 10^23 units, the number equal to the
number of carbon atoms in exactly 12 g of pure C 12
Molar mass : the mass of one mole of a pure
substance.
Avogadro no : 6.022 x 10^23
4. How to calculate :
How to know atomic mass ?! If we have a element
that has 2 isotopes and we want to calculate the
atomic mass we follow the following rule :
Ratio of isotope one * its mass + ratio of isotope 2 *
its mass = no its unit is Amu , also it is written
under the element symbol in the periodic table
Molar mass = Molecular mass = atomic mass in its
magnitude
5. What is the difference between molar
, molecular and atomic mass
Both of them are equal in magnitude but the unit of
atomic mass is Amu and the unit of molar and
molecular mass is g / mole
Another example what is the molar mass of co2 : 12 g /
mole
calculate the molecular mass of water (H2O) (1.01 amu
+ 1.01 amu + 16.00 amu) = 18.02 Amu or 18.02 g / mole
Molar mass of element is no. g / mole . What means ?
Molar mass = mass / Avogadro no ( no of moles )
No of moles = mass / molar mass
6. Some definitions
standard temperature and pressure (STP):standard
temperature is 273.15 kelvins and standard pressure is
760 mm Hg ( 1 atm).
Stoichiometry : the study of the relationships (mass-
mole-volume) among substances involved in chemical
reactions.
dimensional analysis : a name for “equivalent
measures.” A method for solving problems that
involves canceling units.
7. The equation also shows that 2 mol C8H18
react with 25 mol O2 to form 16 mol CO2and 18
mol H2O.
No of mole = mass / molar mass
Density = mass / volume