simple chem q?

Question

how do u noe if H2O appears as liquid state or gaseous state in a reaction, if it is formed as a product?

Answer 1

in a combustion reaction where water is formed its going to be steam, a gas

anytime you have some idea of the temp and pressure of a reaction where water is formed you can just look on a phase diagram for water and tell what state it is supposed to be in.
we all already know that water boils and turns to a gas at normal pressures when its temp gets to 100 deg c. so if a reacation involves combustion and its hot then the water formed in there will be a gas.
if a reaction takes place at room temp and makes water, the water will be liquid.

Answer 2

Technically, it depends on the environment that the reaction occurred. If the reaction occurred at really low temperatures, it could be said that liquid is formed and not vapor. However, if at stardard temperature and pressure most likely, a vapor is formed and especially at room temperature (which is the temperature that most reacitons occur that scientists perform). Most of the time you can't really know unless they tell you in the reaction equation. Normally in a chemical reaction, they denote the products and reactants and what form they are in. For example,
C6H2O6(l) + O2(g)= CO2(g) + H2O(g)
g being gas
l being liquid
s being solid
aq being aqueous.
Most of the time they should tell you the state of water that is formed.

Answer 3

Assuming you're the student, if you put most H20 as (g) in combustion reactions (especially with the larger organic molecules, butane etc) then you'd be correct.
With some reactions, you can't be sure, but you won't get marked down if you do (l) for a couple of equations.

Answer 4

If you are interested in DeltaH etc for standard states, data will refer to liquid water at 25 C. This will often be what you need for thermodynamic calculations.

If a school problem, Q should tell you.

If a real situation, depends on actual conditions of temperature and pressure.