AS Chemistry P2 Prep.

[aaditya menon]

Preventing loss of volatile substances would be reflux. Distillation would be something you do after the reaction is complete to separate the reactants and products. No? At least that's what I thought.

I'm asking not telling btw. I'm pretty confused right now.

Bingo. Both involve a condenser, distillation is a separation technique.

 

[saudha]

oh plsssss guyzzz......u r making others confused 2222

 

[angelgirl:)]

oh plsssss guyzzz......u r making others confused 2222

lol..

 

[angelicsuccubus]

so if u just write reflux... then wat does it mean?

that means "heat under reflux"

 

[SuperGirl123]

Bingo. Both involve a condenser, distillation is a separation technique.

Thanks. Got it now!

 

[angelgirl:)]

that means "heat under reflux"

and if u write for the same reaction warm/heat...den wat does this means?

 

[angelicsuccubus]

"Reflux is a distillation technique involving the condensation of vapors and the return of this condensate to the system from which it originated. It is used in industrial and laboratory distillations. It is also used in chemistry to supply energy to reactions over a long period of time."

 

[angelgirl:)]

"Reflux is a distillation technique involving the condensation of vapors and the return of this condensate to the system from which it originated. It is used in industrial and laboratory distillations. It is also used in chemistry to supply energy to reactions over a long period of time."
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wether its distillation or condensation..or watever ... bascially it means to supply strong heat...isnt it?

 

[TahaJamshed]

so bascially it means to supply strong heat...isnt it?

basically yes but you have to mention weather its reflux or distilled especially in organic

 

[angelicsuccubus]

and if u write for the same reaction warm/heat...den wat does this means?

that means you're giving it heat by radiation or a bunsen burner or a reactor.. or anything.. but not refluxing it, and so if the condition is meant to be reflux, its important that you write reflux.

Organic chem reactions that use heat reflux:

1. Nucleophilic substitution of alcohols with a mixture of red phosphorus and Bromine/Iodine
2. Oxidation of primary alcohols to carboxylic acids
3. Oxidation of secondary alcohols to ketones
4. Nucleophilic substitution of halogenoalkanes with NaOH to form alcohols
5. Nucleophilic substitution of halogenoalkanes with KCN to form nitriles
6. Nitriles forming caboxylic acids using dil. HCl (Hydrolysis)

If I missed anything.. sorry

 

[angelicsuccubus]

wether its distillation or condensation..or watever ... bascially it means to supply strong heat...isnt it?

but it doesn't! If I ask you to supply strong heat to the pot of water on the stove, you are going to increase the flame under the pot, you're not going to reflux it are you?!

Refluxing provides strong heat, but providing strong heat does not mean refluxing.

Because reflux is the name of the technique that uses a column to prevent loss of volatile substances when you are heating them, hence the term "heat with reflux" or "heat under reflux"... It's a refluxing column.

 

[saudha]

anybody wht r the kinetic theory of ideal gases?

 

[angelicsuccubus]

anybody wht r the kinetic theory of ideal gases?

It's a theory which assumes certain things about an ideal gas-------->

• the molecules behave as rigid spheres
• there are no/negligible intermolecular forces between the molecules
• collisions between the molecules are perfectly elastic
• the molecules have no/negligible volume
• the molecules move in random motion
• the molecules move in straight lines
• the kinetic energy of the molecules is directly proportional to the temperature
• the pressure exerted by the gas is due to the collision between the gas molecules and the walls of the container

 

[Muhammad Ahmer Ali]

anybody wht r the kinetic theory of ideal gases?

1)The molecules collide with each other and the walls of container
2)The collisions b/w molecules are perfectly elastic
3)The kinetic energy of the molecules is directly proportional to the temperature.
4*)There is no attractive and repulsive forces b/w molecules
5*)Volume of the gas is negligible compared to the volume of container
(* means important)........

 

[saudha]

thxx

It's a theory which assumes certain things about an ideal gas-------->

• the molecules behave as rigid spheres
• there are no/negligible intermolecular forces between the molecules
• collisions between the molecules are perfectly elastic
• the molecules have no/negligible volume
• the molecules move in random motion
• the molecules move in straight lines
• the kinetic energy of the molecules is directly proportional to the temperature
• the pressure exerted by the gas is due to the collision between the gas molecules and the walls of the container

 

[saudha]

1)The molecules collide with each other and the walls of container
2)The collisions b/w molecules are perfectly elastic
3)The kinetic energy of the molecules is directly proportional to the temperature.
4*)There is no attractive and repulsive forces b/w molecules
5*)Volume of the gas is negligible compared to the volume of container
(* means important)........

thxx

 

[angelgirl:)]

but it doesn't! If I ask you to supply strong heat to the pot of water on the stove, you are going to increase the flame under the pot, you're not going to reflux it are you?!

Refluxing provides strong heat, but providing strong heat does not mean refluxing.

Because reflux is the name of the technique that uses a column to prevent loss of volatile substances when you are heating them, hence the term "heat with reflux" or "heat under reflux"... It's a refluxing column.

thanks aloooot...i got it now very properly...

 

[angelicsuccubus]

thanks aloooot...i got it now very properly...

thank god.. I was beginning to lose it myself XD

 

[angelgirl:)]

but it doesn't! If I ask you to supply strong heat to the pot of water on the stove, you are going to increase the flame under the pot, you're not going to reflux it are you?!

Refluxing provides strong heat, but providing strong heat does not mean refluxing.

Because reflux is the name of the technique that uses a column to prevent loss of volatile substances when you are heating them, hence the term "heat with reflux" or "heat under reflux"... It's a refluxing column.

ok check m/j 2005 Q4 ai...for 2nd stage...its nucleophllic subs.. of halogeno alkne with KCN to from nitril...condtion they wrote heat in ethanol...not reflux...so is wrong?

 

[angelgirl:)]

thank god.. I was beginning to lose it myself XD

lol...