 So this one says how many moles and how many atoms of silicon are there in a sample weighing 10.53 grams Okay, so it asked us how many moles do we have in that much and how many grams do we have or how many atoms? Do we have in that much? Okay, so if you recall do you recall how to get moles from grams? What do you do if you look up at the periodic table, right? And that gives us the what? What's that? molar mass, right? And that converts grams So This is grams of silicon and that helps you out to put that there, you know kind of extends that Conversion factor and we can look up at the periodic table and we look at the molar mass of silicon It's 20.055 And so remember This is just the fast way of writing, right? So what we can do if we really Want to remember, right? So that's grams of silicon per one All of silicon that helps you out to write things like that So remember this is your conversion factor and you can flip this this way or this way So you want to cancel out grams of silicon, right? And you want to get moles of silicon So you're gonna have to put this part at the bottom, right? Is everybody okay with So hopefully you see grams of silicon cancels out there giving us moles of silicon as our units and of course four sig figs is going to be What our answer is to so? So Now we want to figure out. Well, how many atoms are there in that many? Well, we can start from here as we figured out the number of moles of silicon. So let's start from there so We'll say the number of silicon atoms that we have and we know we have 0.3749 moles of silicon atoms Or moles of silicon we'll say and we Hopefully remember you guys remember how many atoms are in one mole? So one mole of silicon atoms is 6.022 times 10 to the 23 silicon So this is just like saying one dozen silicon atoms is 12 silicon So what is this? This is another way of writing something like that a conversion factor So hopefully everybody sees that we're going to make this into a ratio Putting the mole silicon atoms at the bottom Convince that through doing this calculation. We should figure out the number of silicon atoms in the sample Hopefully I don't say I don't see anybody not in there I'm confident and again to four sig figs Should be something around there because this is one-third of one right so this like Everybody okay with that any questions, okay? These are again. These are the really really tough questions from chapter two