Assertion : Pure water obtained from different sources such as river, well, spring, sea etc. always contains hydrogen and oxygen combined in the ratio 1:8 by mass. Reason : A chemical compound always contains elements combined together in same proportion by mass, it was discovered by French chemist, Joseph Proust (1799).

Assertion : Pure water obtained from different sources such as river,

1.	Assertion : Pure water obtained from different sources such as river, well, spring, sea etc. always contains hydrogen and oxygen combined in the ratio 1:8 by mass. Reason : A chemical compound always contains elements combined together in same proportion by mass, it was discovered by French chemist, Joseph Proust (1799).
Answer» If both assertion and reason are true and the reason is the CORRECT explanation of the assertion. If both assertion and reason are true but reason is not the correct explanation of the assertion. If assertion is true but reason is false. If the assertion and reason both are false. Solution :Pure water always contains HYDROGEN and oxygen in the RATIO `1 : 8` by mass. This is in acceleration with the law of constant composition.