What volume of 7.25 mol/L stock solution in needed to make 3.84 L of 8.50 mol/L solution?

4.50 L

Explanation:

First we calculate how many moles are there in 3.84 L of a 8.50 mol/L solution:

Now, keeping in mind that

we can calculate the volume of a 7.25 mol/L solution that would contain 32.64 moles:

So we could take 4.50 L of the 7.25 mol/L solution and evaporate the solvent until only 3.84 L remain.

the answer is c.the valence of the atoms combine .