Question dealing with gravimetric analysis lab.

Question

Approximately how many mL of 5% BaCl₂2H₂O solution would be required to precipitate all the sulfate if we assume that your samples are pure sodium sulfate? Assume that the density of the barium chloride solution is 1.00 g/mL.

If the samples were pure potassium sulfate would you require a smaller or larger volume of barium chloride solution than the amount calculated in the previous question?

Answer 1

There isn't enough information provided to answer the question, but here is the way to do it when you get the rest of the information.

 

First, it helps to write a correctly balanced equation for what is happening:

BaCl₂(aq) + Na₂SO₄(aq) ==> BaSO₄(s) + 2NaCl(aq)

From this equation, you can see that the mole ratio of BaCl2 :  Na2SO4 is 1:1.  So, you want to calculate the moles of Na2SO4 present, but since you didn't give the mass of the sodium sulfate sample, we can't do it.  Once you find moles Na2SO4, that will be = moles BaCl2.  From moles BaCl2, and knowing it is a 5% solution, you can calculate mls of BaCl2 solution needed to get the same number of moles (1:1).