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# arrhenius equation from graph

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Why bother with a post grad course - waste of time? 17-10-2016
1. i need help with this question ..........
first , cant we find the value of -Ea/R just by using the table ???
i did -9.75--5.58 (missing value from table) / (3.41* 10^-3) - (3 * 10^-3)
and i got -10170.73
but the value in the markscheme is -10230

what is wrong with my method if i plot a graph i will find out the gradient by y2-y1 / x2 - x1 anyways

i have one more q concerning the graph (nothing to do with this question tho)....
can we cut the x -axis, for eg. start from 3 * 10^-3 and and also cut the y-axis (becuase the always say that the line must cover half the graph) and still be able to find the y- intercept???????
bcz we neeed to find the a constant from the arrhenius equation, so will it be write to find the y axis interception and put it as the a constant if the axis' are cut ???
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2. (Original post by pondsteps)
i need help with this question ..........
first , cant we find the value of -Ea/R just by using the table ???
i did -9.75--5.58 (missing value from table) / (3.41* 10^-3) - (3 * 10^-3)
and i got -10170.73
but the value in the markscheme is -10230

what is wrong with my method if i plot a graph i will find out the gradient by y2-y1 / x2 - x1 anyways

i have one more q concerning the graph (nothing to do with this question tho)....
can we cut the x -axis, for eg. start from 3 * 10^-3 and and also cut the y-axis (becuase the always say that the line must cover half the graph) and still be able to find the y- intercept???????
bcz we neeed to find the a constant from the arrhenius equation, so will it be write to find the y axis interception and put it as the a constant if the axis' are cut ???
If you chose two points at random you introduce random errors. If you plot the line of best fit you are smoothing off random error ...
3. (Original post by charco)
If you chose two points at random you introduce random errors. If you plot the line of best fit you are smoothing off random error ...
ohh thank you
4. (Original post by pondsteps)
ohh thank you
You want me to plot a graph????
5. (Original post by charco)
You want me to plot a graph????
Nooo, im asking in general... If the graph is cut on both axis not by the same ratio and we extrapolate cos we want to find the y intercept (for the a comstant) is it gonna give the right answer or not?
6. (Original post by pondsteps)
Nooo, im asking in general... If the graph is cut on both axis not by the same ratio and we extrapolate cos we want to find the y intercept (for the a comstant) is it gonna give the right answer or not?
The y- intercept only applies to the y-axis at x=0 ...

y = mx + c (straight line graph)

When x = 0
Then y = c
7. (Original post by charco)
The y- intercept only applies to the y-axis at x=0 ...

y = mx + c (straight line graph)

When x = 0
Then y = c
Ohh so it doesnt matter?
What about if the y axis is cut??

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