## critical temperature of a superconductor

I have this problem here that I don't understand:
The critical temperature of a superconductor, TC varies with the isotopic mass of the element making up the superconductor, M, according to the relation TC *square root(M) = a constant. In lead, TC = 7.184 K for the isotopic molar mass 207.7 g. What is the critical temperature for the isotopic molar mass 136.3 g?

What I did since TC *square root(M) = a constant, I wrote the same formula for the temp we are looking for and said that both equality are equal since a is constant, and then solve for TC(the one we are looking for), but the answer doesn't seem right.
Can you tell me what I am supposed to do? thanks
 Sounds like you're on the right track. What answer did you get?
 I got 5.8196 K but it doesn't seem to be the right answer

## critical temperature of a superconductor

You are right, since if the mass goes down then the TC should go up in order to compensate.

How did you set up the problem? (In mathematical terms so I can see where you went wrong)

I would guess it's a simple algebraic error.
 i pose TC1*square root(M1)= a = TC2*square root(M2) oh! i might have made a mistake of rearranging and solving.now i got 8.868 K
 Yea, that's what I got too.
 Thank you very much