Yazomi
Badges: 18
Rep:
?
#1
Report Thread starter 3 weeks ago
#1
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...
0
reply
golgiapparatus31
Badges: 13
Rep:
?
#2
Report 3 weeks ago
#2
(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?
0
reply
Yazomi
Badges: 18
Rep:
?
#3
Report Thread starter 3 weeks ago
#3
(Original post by golgiapparatus31)
What experiment did you do?
Different concentration of hydrogen and thiosulfate ions reacting together
0
reply
mgi
Badges: 20
Rep:
?
#4
Report 3 weeks ago
#4
(Original post by Yazomi)
Different concentration of hydrogen and thiosulfate ions reacting together
of hydrogen? does not sound likely?!
0
reply
golgiapparatus31
Badges: 13
Rep:
?
#5
Report 3 weeks ago
#5
(Original post by Yazomi)
Different concentration of hydrogen and thiosulfate ions reacting together
What results did you get?
0
reply
golgiapparatus31
Badges: 13
Rep:
?
#6
Report 3 weeks ago
#6
(Original post by mgi)
of hydrogen? does not sound likely?!
He said hydrogen ions, so that's just from an acid
0
reply
Yazomi
Badges: 18
Rep:
?
#7
Report Thread starter 3 weeks ago
#7
(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
0
reply
golgiapparatus31
Badges: 13
Rep:
?
#8
Report 3 weeks ago
#8
(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
0
reply
Yazomi
Badges: 18
Rep:
?
#9
Report Thread starter 3 weeks ago
#9
(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)
0
reply
golgiapparatus31
Badges: 13
Rep:
?
#10
Report 3 weeks ago
#10
(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
Last edited by golgiapparatus31; 3 weeks ago
0
reply
mgi
Badges: 20
Rep:
?
#11
Report 3 weeks ago
#11
(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!
1
reply
golgiapparatus31
Badges: 13
Rep:
?
#12
Report 3 weeks ago
#12
(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
1
reply
Yazomi
Badges: 18
Rep:
?
#13
Report Thread starter 3 weeks ago
#13
(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-
Name:  147ACB38-8553-4EED-AF8C-928F4A53683A.jpg.jpeg
Views: 7
Size:  25.7 KB
(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?
1
reply
Yazomi
Badges: 18
Rep:
?
#14
Report Thread starter 3 weeks ago
#14
(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
0
reply
golgiapparatus31
Badges: 13
Rep:
?
#15
Report 3 weeks ago
#15
(Original post by Yazomi)
Name:  147ACB38-8553-4EED-AF8C-928F4A53683A.jpg.jpeg
Views: 7
Size:  25.7 KB
(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
0
reply
Yazomi
Badges: 18
Rep:
?
#16
Report Thread starter 3 weeks ago
#16
(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!!
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Should there be a new university admissions system that ditches predicted grades?

No, I think predicted grades should still be used to make offers (622)
33.73%
Yes, I like the idea of applying to uni after I received my grades (PQA) (776)
42.08%
Yes, I like the idea of receiving offers only after I receive my grades (PQO) (364)
19.74%
I think there is a better option than the ones suggested (let us know in the thread!) (82)
4.45%

Watched Threads

View All