is it possible to deduce the properties of a compound such as water H2O without resorting to chemical experiments?
Not yet, assuming you mean extrapolating such information from the molecule's structure
Physical and chemical properties are hard enough to extrapolate from a compound's structure, let along its composition. The entire field of theoretical chemistry has been working on predicting the structure-property relationship for several decades. Great strides have been made, but accurate physical property prediction has not been achieved (though I would love to be proven wrong). In most cases, very accurate computation of properties of all but the smallest molecules takes more computing time than you would need to do the experiment.
Your question implies an interest in deriving such properties from the formula. As Canageek said, this is not possible, given the phenomenon of isomerism. One example I just used with my class is that there are 22 known molecules sharing the formula $\ce{C6H12}$, which is a relatively simple formula. Two of the more common are1-hexene and cyclohexane, which you can see have very different structures and properties (chemical and physical).