C h e m I s t r y

Sect ion threeBy:

Youssef Berbar

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

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

What is the difference between molar , molecular and atomic massBoth 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

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.

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

Problem one

Solution of problem one

Mole ratio =

We have 312 moles of ammonia so ,

Problem two

Solution of problem two

Problem Three

Solution of problem Three

Problem four

Solution of problem four

Thanks for listeningYoussef Berbar