give the state symbols of the reaction:

2H2 +O2 =2H2O

hydrogen, and oxygen are gases. when they react, they make steam, a gas.

shouldn't H2O be liquid ?

To determine the state symbols of a chemical reaction, you need to know the physical states of the reactants and products. The state symbols include (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous (dissolved in water).

In the given reaction:
2H2 + O2 = 2H2O

H2 represents hydrogen gas, which is a diatomic molecule in a gaseous state.
O2 represents oxygen gas, which is also a diatomic molecule in a gaseous state.

2H2O represents water, which is in a liquid state.

Therefore, the state symbols for the reaction would be:
2H2 (g) + O2 (g) = 2H2O (l)

air,air,(aq)

or is it gas ?

Who knows...