States of Common Reactants

[angus_grant]

Hey everyone,
what states should I put common organic reactants such as glucose and ethanol as in chemical equations? Ive never figured it out as to whether glucose will be aqueous or a liquid, and the same for any other of the more biological compounds. Thanks in advance! 

[Scooby]

Hey everyone,
what states should I put common organic reactants such as glucose and ethanol as in chemical equations? Ive never figured it out as to whether glucose will be aqueous or a liquid, and the same for any other of the more biological compounds. Thanks in advance! 

Depends on the reaction, but for fermentation glucose and ethanol are both aqueous

[jgoudie]

Here are a couple of other:
- Ester creation the alcohol, carboxylic acid, ester and water are all liquid.
- Combustion reactions
         - Alcohols are generally liquids
         - alkanes/alkenes should be gases unless otherwise stated
         - H2O should be a gas, (when oxidised in a fuel cell it should be liquid)
- As stated above fermentation is an aqueous reaction by nature
- As stated above also reactions involving proteins and carbohydrates happen in the body, thus aqueous would be a fair bet.

Anything random reaction generally they will give you some hints towards what they should be.

Hey everyone,
what states should I put common organic reactants such as glucose and ethanol as in chemical equations? Ive never figured it out as to whether glucose will be aqueous or a liquid, and the same for any other of the more biological compounds. Thanks in advance! 

[angus_grant]

- Ester creation the alcohol, carboxylic acid, ester and water are all liquid.

Does that mean that all the compounds used prior in the synthesis (alkene, chloroalkene, etc) will be liquid too? Thanks, but i'm still a little unsure haha

[jgoudie]

what i meant by that was the generally reaction of:
Alcohol_(l) + Carboxylic Acid_(l) --> Ester_(l) + Water_(l)

Not to sure on the reactants prior to it, in general if they are asking you to go from alkene all the way through to ester, they are worried more about what the reactants, conditions/catalysts are and states shouldn't really be needed, but...

Based around a room temperature reaction (not sure how valid this assumption is...)
Alkenes and Alkanes you can pretty much expect to be gases from C1 -> C4.  above C5 liquids.
Chloro Methane / Ethane with be gas, chloro propane and above you could expect to be liquid.

Does that mean that all the compounds used prior in the synthesis (alkene, chloroalkene, etc) will be liquid too? Thanks, but i'm still a little unsure haha

[Patches]

The states for combustion of a lot of compounds are in the data book too.

Does anyone know the official guide on whether to mark H20 as liquid or gaseous in combustion? I've heard different opinions on whether it's technically correct for the values of delta H given in the data book.

[Limista]

^ it's gaseous.

Combustion reactions usually take place at temperatures greater than 100 degrees Celsius, particularly if they involve alkanes, since alkanes are not very reactive (due to carbon to carbon single bonds, meaning that they are saturated and aligned such that the dispersion forces between these molecules are strong when compared to unsaturated hydrocarbons).

For example, the reaction between ethanol and ammonia is not a combustion reaction, but it still takes place at a temperature of 400 degrees Celsius using alumina catalyst to form ethylamine and water (as a gas) - this just indicates the reaction conditions needed by alkanes to actually react, or it shows you how much temperature is needed to overcome the activation energy barrier of the reaction, so that the reaction can actually proceed.

[brightsky]

^ it's gaseous.

Combustion reactions usually take place at temperatures greater than 100 degrees Celsius, particularly if they involve alkanes, since alkanes are not very reactive (due to carbon to carbon single bonds, meaning that they are saturated and aligned such that the dispersion forces between these molecules are strong when compared to unsaturated hydrocarbons).

For example, the reaction between ethanol and ammonia is not a combustion reaction, but it still takes place at a temperature of 400 degrees Celsius using alumina catalyst to form ethylamine and water (as a gas) - this just indicates the reaction conditions needed by alkanes to actually react, or it shows you how much temperature is needed to overcome the activation energy barrier of the reaction, so that the reaction can actually proceed.

I've heard that you should always write (l). apparently, you assume that after the combustion reactions listed on the data book take place, everything gets cooled to room temperature, at which water is in the liquid state.

[Limista]

I've heard that you should always write (l). apparently, you assume that after the combustion reactions listed on the data book take place, everything gets cooled to room temperature, at which water is in the liquid state.

Really?

Okay, so what would be the states of each of the reactants/products in this case:

2C8H18 + 25O2 --> 18H2O + 16CO2

thanks

[Patches]

I've heard that you should always write (l). apparently, you assume that after the combustion reactions listed on the data book take place, everything gets cooled to room temperature, at which water is in the liquid state.

Yeah that was my question. Intuitively it should obviously be gaseous, but I wasn't sure if the data book values reflected this.

[Scooby]

Really?

Okay, so what would be the states of each of the reactants/products in this case:

2C8H18 + 25O2 --> 18H2O + 16CO2

thanks

They'll accept liquid or gas for both octane and water. Everything else would be gaseous. Never seen an example of where they only accepted only one or the other

If they gave you a heat of reaction value though I'd be checking the Data Book to see whether it matches up with the heat of combustion of liquid octane

[Patches]

Octane is liquid in the data book so they might be strict on that. Otherwise I'm sure it wouldn't matter - just interested really.