i have an exam guys on monday pls can you show me step by step Watch

keyycee
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13.8 grams of salicylic acid is reacted with 18.9 mL of acetic anhydride (CH3CO)2O, in the
presence of 0.4 mL of concentrated sulphuric acid (12.0 M), to give aspirin and acetic acid. Which
reactant is in excess?


MW salicylic acid: 138 gmol-1
MW sulphuric acid 98 gmol-1 density 1.84 g/mL
MW acetic anhydride 102 gmol-1 density 1.08 g/mL

A) Sulphuric acid
B) Salicylic acid
C) Acetic anhydride
D) Aspirin
E) There is no excess of reactant
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charco
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(Original post by keyycee)
13.8 grams of salicylic acid is reacted with 18.9 mL of acetic anhydride (CH3CO)2O, in the
presence of 0.4 mL of concentrated sulphuric acid (12.0 M), to give aspirin and acetic acid. Which
reactant is in excess?


MW salicylic acid: 138 gmol-1
MW sulphuric acid 98 gmol-1 density 1.84 g/mL
MW acetic anhydride 102 gmol-1 density 1.08 g/mL

A) Sulphuric acid
B) Salicylic acid
C) Acetic anhydride
D) Aspirin
E) There is no excess of reactant
Forget the sulfuric acid - it's a catalyst.
For the other two ...
Use the density values to convert volume to mass.
Calculate the moles of each by dividing the mass by the relative mass.
Use the stoichiometric equation to decide which of the components is used up first - this is the limiting reagent
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keyycee
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(Original post by charco)
Forget the sulfuric acid - it's a catalyst.
For the other two ...
Use the density values to convert volume to mass.
Calculate the moles of each by dividing the mass by the relative mass.
Use the stoichiometric equation to decide which of the components is used up first - this is the limiting reagent
i dont know how to work it out thats why i wrote it here
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charco
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(Original post by keyycee)
i dont know how to work it out thats why i wrote it here
I have given you the method ... what don't you understand?
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Rather_Cynical
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Probably your chemistry terms in general I feel she doesn't have a strong grasp on first principles which is why she's struggling.

She needs to know what's going on in the word equation, which tells her salicylic acid and acetic anhydride are reacted together (so they're reagents/reactants) in the presence of sulphuric acid (catalyst).

The products/catalyst can't be the reagents in excess, so aspirin and sulphuric acid could be disregarded.

The only possible answers are B, C, or E.

She needs a balanced chemical equation reacting those things together to work out molar ratios, then figure out if there's an excess of one of them by converting those volumes to number of moles.
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charco
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(Original post by Rather_Cynical)
Probably your chemistry terms in general I feel she doesn't have a strong grasp on first principles which is why she's struggling.

She needs to know what's going on in the word equation, which tells her salicylic acid and acetic anhydride are reacted together (so they're reagents/reactants) in the presence of sulphuric acid (catalyst).

The products/catalyst can't be the reagents in excess, so aspirin and sulphuric acid could be disregarded.

The only possible answers are B, C, or E.

She needs a balanced chemical equation reacting those things together to work out molar ratios, then figure out if there's an excess of one of them by converting those volumes to number of moles.
Why do you assume that the OP is female?
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Andy98
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(Original post by charco)
Why do you assume that the OP is female?
I suspect it was something to do with username sounding like "Kasey"...

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