Moles and Laws of Chemistry

Mole
Mole is the unit we use to measure the amount of chemicals we have.
The number of particles in any substance present in 1 mole is =
6.022*10^23

The number of moles in a sample =
Mass of that element or compound/ Molecular or atomic mass

Examples:

Find the mass of 1 mole of hydrogen
Mass of 1 hydrogen molecule = 2 units
1 mole = mass/2
Mass of 1 mole of hydrogen = 2g.
— This means that there are 6.022*10^23 molecules in 2g of hydrogen.

Find the mass of 1 mole of oxygen
Mass of 1 oxygen molecule = 32 units
1 mole = mass/32
Mass of 1 mole of oxygen = 32g.

Find the mass of 1 mole of water
Mass of 1 water molecule = 18 units
1 mole = mass/18
Mass of 1 mole of oxygen = 18g.

Find the mass of 1 mole of calcium oxide
Mass of 1 calcium oxide molecule = 26 units
1 mole = mass/26
Mass of 1 mole of calcium oxide = 26g.

Find the mass of 1 mole of carbon dioxide
Mass of 1 carbon dioxide molecule = 44 units
1 mole = mass/44
Mass of 1 mole of carbon dioxide = 44g.

Find the number of atoms in 0.2 moles of oxygen
1 mole = 16g of oxygen atoms
0.2 moles = 3.2g of oxygen atoms
— This means that 2/10th of 6.022*10^23 oxygen atoms weigh 3.2g.

, Find the number of molecules in 0.5 moles of water
1 mole = 18g of water molecules
0.5 moles = 9g of water molecules

Find the number of molecules in 2 moles of hydrogen
1 mole = 2g of hydrogen molecules
2 moles = 4g of hydrogen molecules

Find the number of atoms in 4 moles of potassium
1 mole of potassium = 39g of potassium atoms
4 moles of potassium = 156g of potassium atoms

Find the number of atoms in 0.8 moles of chlorine
1 mole = 36g of chlorine atoms
0.8 moles = 40g of chlorine atom


Laws of Chemistry
Law 1 - Law of conservation of mass
The mass of reactants and their product is the same.
However, little mass is lost in sources like heat.
Example 1 - C + O2 = CO2, 12 + 32 = 44 (mass of CO2)
Example 2 - H2 + O = H2O, 2 + 16 = 18 (mass of H2O)
Example 3 - H2 + S + O4 = H2SO4, 2 + 32 + 64 = 98 (mass of H2SO4)
Example 4 - S + O2 = SO2, 32 + 32 = 64 (mass of SO2)
Example 5 - Ca + O = CaO, 40 + 16 = 56 (mass of CaO)
Example 6 - Cu + S + O4 = CuSO4, 64 + 32 + 64 = 160 (mass of CuSO4)
Example 7 - Na + Cl = NaCl, 23 + 35 = 58 (mass of NaCl)
Example 8 - Ca + (OH)2 = Ca(OH)2, 40 + 34 = 74 (mass of Ca(OH)2)
Example 9 - Fe2 + O3 = Fe2O3, 112 + 48 = 160 (mass of Fe2O3)
Example 10 - C + H4 = CH4, 12 + 4 = 16 (mass of CH4)

Law 2 - Law of definite proportion
The ratio of elements in a compound is fixed.
Example 1 - CO2
1 molecule of CO2 - 1 carbon atom and 2 oxygen atoms - 12g and 32 g
- 3:8
4 molecules of CO2 - 4 carbon atoms and 8 oxygen atoms - 48g and
128g - 3:8
Example 2 - H2O