The combination of elements to formed compound is governed by the below five laws
Law of Conservation of Mass
It states that mass remains conserved.
For radioactive and nuclear reactions, 1st law is modified – Law of Conservation of mass & energy.
Law of Conservation of Mass & Energy:
It status that during chemical reaction sum of mass & energy is conserved.
Example
C + O2 -> CO2
12 + 32 12 + (16)
44 gm 44 gm
Mass of Reactants = Mass of Products
Law of constant or definite proportion
It states that elements combine in their definite proportion of mass to give compounds.
Example
CO2 -> C : O
12 : 32
3 : 8
H2O H : O
2: 16
1: 8
Law of Multiple Proportion:
It states that when two different elements combined to form more than one compound and if mass of one element is fixed then other elements mass bears simple whole no. ratio.
Example
NO 14:16 28: 32
NO2 14:32 28: 64
N2 O4 28 :64 28: 64
N2 O5 28:80 28: 80
Now, ratio of oxygen:
=32: 64: 64: 80
= 2: 4: 4: 5
CO 12: 16
CO2 12: 32
Now ratio of Oxygen
=16: 32= 1: 2
PO2 16: 32
PO5 16: 80
Now Ratio of O
=32: 80=2: 5
Gay Lassac Law of Gaseous
When gases combine, they bear simple whole no. ratio of their volumes provided all the gases are at the same temperature and pressure
Example
1 N2 + 3H2 -> 2N H3 (Haber’s Process)
Ratio 1:3. So 100 ml of Nitrogen combines with 300 ml of oxygen to form 200ml of Ammonia
H2 + I2 -> 2H I (Hydrogen Iodide)
Ratio 1:1. So 100 ml of hydrogen combines with 100 ml of Iodine to form 200ml of Hydrogen Iodide
AVAGADRO LAW: -
It states that equal volume of gases at the same temperature and pressure should contain equal no. of molecules.
Extra reading
Law of Reciprocal Proportion:
It states that when two different elements combine with fixed mass with 3rd element & when their ratio are compound when they combine with each other, bears simple whole no.
