Urgent help chemistry

This question is about the reaction between hydrogen sulfide (H2S) and oxygen. The equation for the reaction is:
2 H2S(g) + 3 O2(g) → 2 H2O(g) + 2 SO2(g) (a) What does H2O(g) represent?
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(1)
(b) Calculate the volume of oxygen required to react with 50 cm3 of hydrogen sulfide.
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