coconut64
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Hajra Momoniat
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Because H2SO4 is a strong acid and so you want to minimise the level of hazard. That's the only reason I can think of but good question though
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coconut64
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(Original post by Hajra Momoniat)
Because H2SO4 is a strong acid and so you want to minimise the level of hazard. That's the only reason I can think of but good question though
I heard that it is something to do with the heating though? No?
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Hajra Momoniat
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Im not sure about that
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alow
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(Original post by coconut64)
I heard that it is something to do with the heating though? No?
What's the boiling point of conc. sulfuric acid?
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coconut64
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(Original post by alow)
What's the boiling point of conc. sulfuric acid?
337 °C according to Google, but I don't know what difference there is between concentrated acid and dilute acid...

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alow
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(Original post by coconut64)
337 °C according to Google, but I don't know what difference there is between concentrated acid and dilute acid...

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Dilute will be in water.

Sulfuric acid starts to decompose at around 300 Celsius.
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coconut64
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(Original post by alow)
Dilute will be in water.

Sulfuric acid starts to decompose at around 300 Celsius.
So the reagents need to be aqueous and since the concentrated acid is not aqueous, dilute acid is used instead?

Sulfuric acid starts to decompose at around 300 Celsius - > what does this suggest as the reaction is heated under reflux regardless of whether the acid is dilute or not...

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alow
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(Original post by coconut64)
So the reagents need to be aqueous and since the concentrated acid is not aqueous, dilute acid is used instead?

Sulfuric acid starts to decompose at around 300 Celsius - > what does this suggest as the reaction is heated under reflux regardless of whether the acid is dilute or not...

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What temperature will the dilute acid boil at?
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coconut64
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(Original post by alow)
What temperature will the dilute acid boil at?
Not sure, but google said the the more dilute it is, the closer it is to 100 degrees. The more concentrated the acid, the higher the boiling point. But I am very lost now.
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alow
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(Original post by coconut64)
Not sure, but google said the the more dilute it is, the closer it is to 100 degrees. The more concentrated the acid, the higher the boiling point. But I am very lost now.
So dilute boils at about 100 degrees and concentrated at 337 degrees.

Sulfuric acid starts decomposition at 300 degrees.

Which of dilute and concentrated do you therefore not want to reflux?
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coconut64
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(Original post by alow)
So dilute boils at about 100 degrees and concentrated at 337 degrees.

Sulfuric acid starts decomposition at 300 degrees.

Which of dilute and concentrated do you therefore not want to reflux?
So dilute acid is better because you don't want it to decompose. Okay

Does this mean that for all reactions that are heated under reflux, if acid is used as a catalyst it is must be dilute? But for the decomposition bit, do most acid decompose at 300 degrees ?

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alow
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(Original post by coconut64)
So dilute acid is better because you don't want it to decompose. Okay
Yeah. Also if you have to dissolve whatever you're oxidising, this may work better with water present than in conc. acid.

Does this mean that for all reactions that are heated under reflux, if acid is used as a catalyst it is must be dilute? But for the decomposition bit, do most acid decompose at 300 degrees ?

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Not necessarily.

No idea, but I very much doubt it.
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username986184
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(Original post by coconut64)
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Conc. sulphuric is dehydrating
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Fengaleng
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Looking at the reaction as an equilibrium:
(H2S04)
CH3CH2OH↽−−⇀CH2=CH2+H2O

If the sulphuric acid is conc. , there is little presence of water and so the equilibrium will shift to the right and as a result ethanol will be dehydrated.

Whereas, if it was dilute, there is a greater concentration of water and as a result the equilibrium would shift left to form more ethanol.
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