The law states that in a chemical compound
Two or more elements are always present in same ratio by mass
It does not matter where the compound came from or who prepared it.
Water (H 2 O) is a chemical compound.
It contains 2 elements; Hydrogen and Oxygen
These 2 elements are present in constant proportion by mass which is of 1 :8
(Since Mass of H 2 = 2g and O=16g, therefore H 2 :O = 2:16 = 1:8)
It means that in 9 grams of Water
There will always be 1 gram of Hydrogen and 8 Grams of Oxygen
It does not matter what the source of water is (rain water/tap water/sea water) or how the water was prepared (melting of ice/cooling of water vapour)
SAMPLE PROBLEM 2,3,4 LS
In text Question - Page 33 Q2
NCERT Question - Q2