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Biology rate of reaction question

Can anyone help? ImageUploadedByStudent Room1448794691.769753.jpg
I don't understand how the answer is 2.5


Posted from TSR Mobile
Show me the markscheme.
It's 2.5g/dm^3/min, you might be working it out in g/dm^3/s instead
In short, convert the seconds to minutes and you'll have the answer
(edited 8 years ago)
Rate of reaction = difference in x-axis / difference in y-axis
so = (doesn't matter where) 240s / 10 dgm-3
so = 24 s-1dmg-3 (not sure about unit I've given)
Could also do 120 / 5, 60 / 2.5 usw. usf.

I just picked the most obvious sizes to me.

Edit: Also, there isn't only one unit you can use, but the values and the unit used must correspond.

So if you changed dm3 to cm2, you must times the value by 100.
(edited 8 years ago)
Reply 5
Avatar for jamestg
jamestg
21
Original post by elise68
Can anyone help? ImageUploadedByStudent Room1448794691.769753.jpg
I don't understand how the answer is 2.5


Posted from TSR Mobile


Just basic gradient calculation, as the above poster said (change in y/change in x)

so 25/10

getting 2.5 :smile:
Original post by XcitingStuart
Rate of reaction = difference in x-axis / difference in y-axis
so = (doesn't matter where) 240s / 10 dgm-3
so = 24 s-1dmg-3 (not sure about unit I've given)


I'm fairly sure it's the difference in y-axis over the difference in x-axis. We're looking at the rate of change of concentration with respect to time. Not the other way around...
Original post by jamestg
Just basic gradient calculation, as the above poster said (change in y/change in x)

so 25/10

getting 2.5 :smile:


Where did you attain the 25 and the 10 from the graph? :biggrin:
Reply 8
Avatar for Ayman!
Ayman!
15
Remember that the rate of reaction is just the gradient of the graph in this case.
Original post by yasaminO_o
It might be 2.5g/dm^3/min, you might be working it out in g/dm^3/s instead
In short, convert the seconds to minutes and you'll have the answer


This is the correct answer.

Convert all the seconds to minutes.

120 seconds is 2 minutes.

5 / 120 = 2.5.
Original post by High Stakes
Where did you attain the 25 and the 10 from the graph? :biggrin:


Sh*t :biggrin: - my excuse is that I only nipped in here to see what the problem was to escape mock revision for a few minutes
Original post by jamestg
Sh*t :biggrin: - my excuse is that I only nipped in here to see what the problem was to escape mock revision for a few minutes


Haha, no worries. :smile: Get back to revision!! I should too (been taking a break for 30 minutes). Think I'll try some M1 and C4 and Chemistry.

jamestg - A*AAA <--- You're on my list. :colone:
Original post by High Stakes
I'm fairly sure it's the difference in y-axis over the difference in x-axis. We're looking at the rate of change of concentration with respect to time. Not the other way around...


Oops. :colondollar:

(I seem to be doing this a lot recently, like telling the wrong things [if I am.])
(I presume you have more authority in this subject, considering you look like you have a greater understanding of what we're talking about.)

Sorry OP if I'm wrong.

Ty for correction @High Stakes.
(edited 8 years ago)
Original post by XcitingStuart
Oops. :colondollar:

(I seem to be doing this a lot recently, like telling the wrong things [if I am.])
(I presume you have more authority in this subject, considering you look like you have a greater understanding of what we're talking about.)

Sorry OP if I'm wrong.

Ty for correction @High Stakes.


No worries at all. :smile: Just remember that when we're calculating a gradient, we want to see how our dependent variable changes with respect to our independent variable.

For example we can see how the concentration of a product changes as time. But not the other way around.
Original post by High Stakes
Haha, no worries. :smile: Get back to revision!! I should too (been taking a break for 30 minutes). Think I'll try some M1 and C4 and Chemistry.

jamestg - A*AAA <--- You're on my list. :colone:


Hahaha, luckily the A* is for maths and not biology :wink:

So close to finishing my 7 hours of biology, then onto a few hours of politics and then finally C1 until bedtime - ugh mocks
Original post by jamestg
Hahaha, luckily the A* is for maths and not biology :wink:

So close to finishing my 7 hours of biology, then onto a few hours of politics and then finally C1 until bedtime - ugh mocks

In one day!?

Seems kind of excessive :s-smilie:
Original post by DavidYorkshireFTW
In one day!?

Seems kind of excessive :s-smilie:


Nah over two days broken into 90minute bursts

Produced a lot of revision resources as well so I'm feeling fairly confident about my mock.
Reply 17
Avatar for Kozmo
Kozmo
10
Just out of curiosity, does the mark scheme allow answers if it's per second?

Rate of reaction can be in any given time, so I'm assuming it does.

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