Why is it difficult to obtain oxygen from water

Acompound is found to contain 6.1% hydrogen and 93.9% oxygen. find it’s empirical formula.

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

What state of matter is ice a. liquid b. element c. solid d. gas