Why do we often write the water product as a gas in complete combustion reactions?

Answer 1

Let's put it this way, then.

The majority of combustion reactions are exothermic, which means they release heat. This can be represented as follows:

#"Hydrocarbon"(l"/"g) + "O"_2(g) -> "CO"_2(g) + "H"_2"O"(g) + Delta#
where the hydrocarbon is generally a liquid if it is massive (larger than butane, usually), and is generally a gas if it is small. #Delta# on the products side would represent the heat released due to the reaction itself.
Since water is produced, the water can immediately absorb that heat. #"CO"_2# at room temperature is a gas, but water at room temperature is a liquid.
So although #"CO"_2# could absorb some of the heat, water also absorbs the heat that is produced in such a short amount of time.
The heat has a greater effect on the water, since the liquid water molecules had less energy to begin with than the gaseous #"CO"_2# molecules, so water is a gas when the combustion reaction first finishes.

It is true that water vapor could condense onto the insides of a bomb calorimeter in a closed system, but we usually only discuss the instants following the reaction.

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Answer 2

Water is written as a gas in complete combustion reactions because in most cases, combustion reactions occur at high temperatures, causing water to vaporize into steam. This representation helps to show that water is in its gaseous state at these elevated temperatures, rather than as a liquid. Additionally, writing water as a gas helps to balance the chemical equation properly.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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