To make 100. mL of a solution that is 0.25 M in chloride ion, how many grams of magnesium chloride would you need to dissolve?
I had a few different approaches to this, but my most immediate thought was to think of each element (monoatomic or polyatomic) as a part of a larger compound. Therefore, molarity of the chloride ion is 0.25, which is 0.66 moles of the entirety of the compound; the rest being magnesium.
This approach led me to 3.52 grams, since I have 0.037 moles (molarity is 0.037 moles/liter). However, the answer is 1.2 grams.
What am I doing wrong?