A student collected three samples of water from different sources and found out the percentage of hydrogen and oxygen by mass in thse samples. It should have been 1 : 8 by mass. But it was different in all three samples, Moreover, the values did not match
(i) In your opinion why did the student get different results for different samples ?
(ii) What should have been done by him ?
(iii) Which law of chemical combination is supported by these observations
(iv) How will you check the purity of water in the laboratory ?

Explanation

(i) The student got different results for different samples because they were not pure
(ii) He should have purified these samples by suitable methods before performing the experiment
(iii) These observations are supported by the law of constant composition according to which the chemical compound to be estimated must be completely pure.
(iv) Purity of water in the laboratory can be checked by determining its boiling point. For pure water, it must be `100^(@)C`.