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# Chemistry rate of reaction help watch

1. Situation: Reactant A with reactant B with excess

If there was 50cm^3 of reactant A with B in excess and 25cm^3 of reactant A with B in excess. Everything is the same except the volumes. Which would react faster? My teacher says A but wont say why and I don't get why, I thought they'd be the same.
2. I really don't get this, wouldn't it be the same?
3. Obvious A if you have double the volume of solution A. More particles available to react. It should be around double the rate.

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4. (Original post by TheAJK)
Situation: Reactant A with reactant B with excess

If there was 50cm^3 of reactant A with B in excess and 25cm^3 of reactant A with B in excess. Everything is the same except the volumes. Which would react faster? My teacher says A but wont say why and I don't get why, I thought they'd be the same.
Define react faster.
A has a higher concentration at double the volume (considering B is in excess)
Collision theory states a reaction is more likely to occur with higher concentrations, however to get to completion the story is different.
5. A has a higher concentration.

(Original post by Hart1995)
Obvious A if you have double the volume of solution A. More particles available to react. It should be around double the rate.

Posted from TSR Mobile

Not necessarily double the volume. You could have double the volume and still have the same concentration as what you would have with the original A.

Concentration is the key factor, not volume.
6. (Original post by James A)
A has a higher concentration.

Not necessarily double the volume. You could have double the volume and still have the same concentration as what you would have with the original A.

Concentration is the key factor, not volume.
The situation is the concentration is the same, this is what I don't understand.
7. Well there would be more A particle for B to collide and react with so the overall reaction would be faster.
Imagine it like this, in one scenario there were 50 girls and an excess of boys walking around in one room and in the other there were 25 girls and an excess of boys walking around in one room. In both scenarios, the room size is the same so in which one would it be more likely for a boy to walk into, or collide with a girl?
8. (Original post by TheAJK)
The situation is the concentration is the same, this is what I don't understand.
You said everything is the same, which means that the concentration is the same.

Looking back at it again, I would say neither.

Because the rate of reaction depends on concentration, not volume.

So regardless of the volume used, the concentration remains the same, hence why I'm saying that neither reaction is faster than the other.

Volume, does not affect the rate of reaction.

(Original post by Jodie_668)
x
10. (Original post by James A)
You said everything is the same, which means that the concentration is the same.

Looking back at it again, I would say neither.

Because the rate of reaction depends on concentration, not volume.

So regardless of the volume used, the concentration remains the same, hence why I'm saying that neither reaction is faster than the other.
That is my point but he says I'm wrong I don't get it.
11. (Original post by TheAJK)
That is my point but he says I'm wrong I don't get it.
12. (Original post by TheAJK)
That is my point but he says I'm wrong I don't get it.
If B is said to be in excess then the conc. of A compared to the conc. of B has increased if the volume is increased.
13. (Original post by joostan)
If B is said to be in excess then the conc. of A compared to the conc. of B has increased if the volume is increased.
Ohhhhh, well that does make sense. He said 'in this case' so he could be referring to B being in excess.
14. (Original post by James A)
I did thanks
15. (Original post by TheAJK)
Ohhhhh, well that does make sense. He said 'in this case' so he could be referring to B being in excess.
You're teacher is unlikely to have lied to you, unless they're consistently wrong I'd assume they're right
16. (Original post by joostan)
You're teacher is unlikely to have lied to you, unless they're consistently wrong I'd assume they're right
No he's always right but he was a in rush and couldn't explain it in time so he said he'll tell me Tuesday but it's been bothering me, thank you!
17. (Original post by TheAJK)
No he's always right but he was a in rush and couldn't explain it in time so he said he'll tell me Tuesday but it's been bothering me, thank you!
No worries
18. (Original post by TheAJK)
x
(Original post by joostan)
If B is said to be in excess then the conc. of A compared to the conc. of B has increased if the volume is increased.
Your statement only holds true if the moles of both A solutions were different. The question stated that everything was kept the same (implying that moles was kept the same). The only thing changed of course, was the volume. Therefore despite the volumes being different, the concentration of the solution changes.

Have you dealt with the n=c*v/1000 formula?

19. (Original post by James A)
Your statement only holds true if the moles of both A solutions were different. The question stated that everything was kept the same (implying that moles was kept the same). The only thing changed of course, was the volume. Therefore despite the volumes being different, the concentration of the solution changes.

Have you dealt with the n=c*v/1000 formula?

Yes, that was what I originally thought. Guess I'll just have to wait and ask him, I'll post the outcome. Thanks all!
20. (Original post by TheAJK)
Yes, that was what I originally thought. Guess I'll just have to wait and ask him, I'll post the outcome. Thanks all!
You're welcome!

Have you got another chemistry teacher you could ask too?

Make sure that when you ask your teacher again, you make sure that the question says that everything else is kept the same (i.e. moles).

But please clarify if the concentrations are kept the same or not (from your initial question)!

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Updated: March 22, 2013
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