Calculating Curie Constant for Iron Ammonium Alum using Curie's Law

[AStaunton]

HI there..

The problem is given the below table for iron ammonium alum find C the Curie constant for this material..

T(in kelvin).....X_m
15......(129*10^-4)
100......(19.4*10^-4)
200......(9.7*10^-4)
300......(6.5*10^-4)

as X = C/T I thought simply rearrange:
=> XT = C

and so take any two values from above table and plug them into equation:
=> C = 15*(129*10^-4)K.A/T.m ---------where 15 and (129*10^-4) are taken from above table...

However, this is not the correct value for the curie constant for this material...
Can anyone please tell me where I am going wrong?

Thanks

Andrew

 

[rock.freak667]

It would be better to plot a graph of X vs 1/T. The gradient of that line will give you C.

 

[AStaunton]

Thanks for your reply...
using your method of plotting X V 1/T the value for C (curie constant) I get is around 0.2...however, this is not in agreement with the answer that I have been provided with.. so am i perhaps overlooking a subtlety in the question?...the only information provided was the table I gave in the previous post...

 

[rock.freak667]

What was the value you are given?

 

[AStaunton]

It was incorrect to say I was given an answer...It is an online problem and all it tells is if an answer is right or wrong, and according to this, C=0.2 is not correct..
There is also another equation associated with C:

M=C*B/T

Would it be possible to use this to find value of C?
ie. is there some way of find M,B and T using the table I already posted?

Cheers

 

[rock.freak667]

M=C*B/T

I assume M is the same as X_m, if that is the case then you cannot get the value of C without knowing values of B for the same T.

If the relation you are given was X_m=C/T then that 'C' is not the same C as above.