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Chemistry help

The question
From your result, suggest the experimental evidence that this reaction proceeds by more than one step.
Overall equation for this reaction
S2O3^2- + 2H^+ -> S + SO2 + H2O

What I was thinking was that the result shows as the concentration of reactants increases, so does the initial rate- what’s shown in the experiment. But I’m not certain whether this would be sufficient to as evidence for a multi-step reaction.

Text book wise it would say that it’s because there’s too many molecules to react with eachother at the right orientation and collide successfully in one step but evidence from experiment...
Original post by Yazomi
The question
From your result, suggest the experimental evidence that this reaction proceeds by more than one step.
Overall equation for this reaction
S2O3^2- + 2H^+ -> S + SO2 + H2O

What I was thinking was that the result shows as the concentration of reactants increases, so does the initial rate- what’s shown in the experiment. But I’m not certain whether this would be sufficient to as evidence for a multi-step reaction.

Text book wise it would say that it’s because there’s too many molecules to react with eachother at the right orientation and collide successfully in one step but evidence from experiment...

What experiment did you do?
Reply 2
Avatar for Yazomi
Yazomi
OP
21
Original post by golgiapparatus31
What experiment did you do?


Different concentration of hydrogen and thiosulfate ions reacting together
Reply 3
Avatar for mgi
mgi
20
Original post by Yazomi
Different concentration of hydrogen and thiosulfate ions reacting together

of hydrogen? does not sound likely?!
Original post by Yazomi
Different concentration of hydrogen and thiosulfate ions reacting together

What results did you get?
Original post by mgi
of hydrogen? does not sound likely?!

He said hydrogen ions, so that's just from an acid
Reply 6
Avatar for Yazomi
Yazomi
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21
Original post by golgiapparatus31
What results did you get?


For both-
As the concentration increases the initial rate increases.
Volume is the same throughout
The time take for the whole reaction to take place decreases
^when the cross is no longer visible
Original post by Yazomi
For both-
As the concentration increases the initial rate increases.
Volume is the same throughout
The time take for the whole reaction to take place decreases
^when the cross is no longer visible

Great.

So what order of reaction did you find wrt to each reactant?

From this can you suggest a rate equation?

From this can you suggest a rate-determining step?

From this can you deduce that this reaction proceeds by more than one step?

Have a think at each question in turn and let me know what you think
Reply 8
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Yazomi
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21
Original post by golgiapparatus31
Great.

So what order of reaction did you find wrt to each reactant?

From this can you suggest a rate equation?

From this can you suggest a rate-determining step?

From this can you deduce that this reaction proceeds by more than one step?

Have a think at each question in turn and let me know what you think


Both reactant is to the first order

Rate = K[S2O3^2-][H^+]

Would a rate determining step be something like
Na2S2O3 -> S2O3^2- + 2Na
HCl -> H^+ + Cl^-

( I could only deduce this from the overall equation given by the pag tho)
Original post by Yazomi
Both reactant is to the first order

Rate = K[S2O3^2-][H^+]

Would a rate determining step be something like
Na2S2O3 -> S2O3^2- + 2Na
HCl -> H^+ + Cl^-

( I could only deduce this from the overall equation given by the pag tho)

The equations are wrong

Rate equation is
Rate = k[S2O3^2-][H^+]
Rate determining step will involve 1 species of each one reacting:
so S2O32- + H+ -> HS2O3-

But the overall equation is S2O3^2- + 2H^+ -> S + SO2 + H2O

Rate equation involves only 1 H atom, but overall equation has 2 H atoms

so there must be more steps
(edited 3 years ago)
Reply 10
Avatar for mgi
mgi
20
Original post by golgiapparatus31
He said hydrogen ions, so that's just from an acid

he did not actually say hydrogen ions to be fair!
Original post by mgi
he did not actually say hydrogen ions to be fair!

He said "hydrogen and thiosulfate ions". I agree that "hydrogen ions and thiosulfate ions" is clearer
Reply 12
Avatar for Yazomi
Yazomi
OP
21
Original post by golgiapparatus31
The equations are wrong

Rate equation is
Rate = k[S2O3^2-][H^+]
Rate determining step will involve 1 species of each one reacting:
so S2O32- + H+ -> HS2O3-

But the overall equation is S2O3^2- + 2H^+ -> S + SO2 + H2O

Rate equation involves only 1 H atom, but overall equation has 2 H atoms

so there must be more steps where the overall reaction of those steps is an H+ reacting with HS2O3-


147ACB38-8553-4EED-AF8C-928F4A53683A.jpg.jpeg
(Would this be right with the first one being the rate determining step?)
How would this be experimental evidence to determine there’s more than one step?
Reply 13
Avatar for Yazomi
Yazomi
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21
Original post by mgi
he did not actually say hydrogen ions to be fair!


Sorry for the misunderstanding, it’s meant to be hydrogen ions and thiosulfate ions
Original post by Yazomi
147ACB38-8553-4EED-AF8C-928F4A53683A.jpg.jpeg
(Would this be right with the first one being the rate determining step?)
How would this be experimental evidence to determine there’s more than one step?

First step is ok
Second one is too
Third should be H2SO3 -> S + SO2 + H2O
so when you add the 3 steps, you get the overall eqn

The rate equation shows that the rate determining step is H+ + S2O32- -> HS2O3-
This isn't the same as the overall equation, so the equation must be a multistep reaction

Overall equation has 2 H atoms on each side
RDS has only 1 H atom
so need more steps to reach same as overall
Reply 15
Avatar for Yazomi
Yazomi
OP
21
Original post by golgiapparatus31
First step is ok
Second one is too
Third should be H2SO3 -> S + SO2 + H2O
so when you add the 3 steps, you get the overall eqn

The rate equation shows that the rate determining step is H+ + S2O32- -> HS2O3-
This isn't the same as the overall equation, so the equation must be a multistep reaction

Overall equation has 2 H atoms on each side
RDS has only 1 H atom
so need more steps to reach same as overall


Ahhhh I understand now thanks for all the help!!

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