[Big-Daddy]

I don't know if I'm missing something big but I don't know how to get to the bottom of this problem:

In a mixture of MgCl2 and Mg(NO3)2, Mg constitutes 21.25% of the total mass. What percent of the total mass does MgCl2 constitute?

I thought this problem is a simple Mr scale-up, Mr[MgCl2]/Mr[Mg] * f(Mg) = f(MgCl2), but then of course I realized that Mg is contributed by both Mg(NO3)2 and MgCl2, not just MgCl2, leaving me not knowing how to solve.

[Rutherford]

Assume the mass of the mixture to be 100g and that masses (or moles if you like) of MgCl2 and Mg(NO3)2 are x and y, then make a system of equations and solve it.

[Big-Daddy]

Thanks for the advice. Did you get 53.19% ?

[Rutherford]

That should be it.