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=
`(4.23)/(1.65)* {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