Question

How much fluorine (in grams) does the second sample produce?

I divided 2.58kg of fluorine by the 1.24kg of magnesium, but I'm not sure that's the right way to do this. Should I cross multiply? I read the page in the book, and it had nothing to do with a problem like this.

Answer 1

Answer: 1.94 kg

Explanation: Given : $MgF_2\rightarrow Mg+F_2$

Sample 1 produces 1.65 kg of Mg and 2.58 kg of $F_2$.

As every chemical reaction follows law of conservation of mass, which says that the mass of products must be equal to the mass of reactants.

Thus mass of $MgF_2$ should be 1.65+2.58 kg = 4.23 kg

1.65 kg of Mg was produced by 4.23 kg of $MgF_2$

Now the second sample produces 1.24 kg of Mg.

1.24 kg of Mg will be produced by=$\frac{4.23}{1.65}\times {1.24}=3.18 kg$

Now again law of conservation of mass is to be followed so mass of $F_2$ will be= mass of $MgF_2$ - mass of $Mg$

=(3.18 kg -1.24 kg)  = 1.94 kg