How many grams of lithium chloride do we need to add in order to prepare 450 millilitres of a 1.4 molar solution? So a couple of things here, one, we know the substance we're dealing with. We've got lithium chloride. And, remember that when we talk about molarity, what we really mean is for this will be 1.4 moles per litre, so moles of lithium chloride per litre of solution. So, thinking about molarity in terms of this expanded unit can help us figure out how we're going to set this problem up. So, let's first come up with a plan of how we're going to get to our answer. We know we want grams of lithium chloride at the end, and if I want to get to grams, I know I can get there from moles of lithium chloride because I can figure out what the molar mass is for that particular substance. And so, I've got to look here and figure out how am I going to get to moles of lithium chloride. Well, notice that I'm given this relationship between the moles and the volume of lithium chloride in the terms of the molarity. And so, if I have the volume of my lithium chloride. Then I can get two moles of lithium chloride, which can get me two grams of lithium chloride. So, the first we want to do is actually find the molar mass of our lithium chloride. So, lithium has a mass of 6.94, chlorine 35.45. And we get a molar mass of 42.39 grams per mole. And so, I'm going to be able to use that later in my problem to get to the final answer. So the first thing I'm going to start with, is my 450 millilitres. And I'm going to have to convert that to liters because I notice that molarity is in moles per liter. So, 1,000 millilitres in 1 liter. Then, I'm going to use my molarity to get from my volume to my moles. So, 1.4 moles of lithium chloride per liter. Now, I have moles on top. I'm going to put moles on the bottom and grams on top here. 42.39 grams per mole, because again I want to make sure my units are cancelling out. And that's what I'm actually going to do now, is go back through and see that millilitres cancels with millilitres, liters cancel, moles cancel, and what I'm left with are units of grams. And that's what I'm looking for in the problem. And when I do the math, what I end up with is 26.7 grams of lithium chloride. But I need to round this to two significant digits, so I'll have 27 grams of lithium chloride.