<p>So i really want to get an A in chemistry next semester, so I'm doing a bit of self studying of chemistry and I'm using Schaum's guide, and while it's an excellent book so far and I'm not having too much trouble with most of the problems, it seems like either their math or mine is off (if it is my math, then I can't find my error)....can anybody who has the book show me how they arrived at their solutions for problems 35, 37, and 39 of chapter 2?</p>
<p>or if you're good at chemistry, I can post the problems and you can post a solution?</p>
<p>A certain public water supply contains .1 ppb of chloroform, CHCl3. How many molecules of CHCl3 would be contained in a .05 mL drop of this water?
2.5X10^10</p>
<p>The threshold after which death occurs is 2500 nanograms cyanide per mL of blood. Assuming the average blood volume of 5.6L for an average sized person, how many moles of KCN will provide the fatal dose, and how many molecules would provide the fatal dose?
2.6X10^-4, 1.6X10^20</p>
<p>Never mind about the other problem I mentioned, I was looking at the wrong problem.</p>
<p>I love that book, but I don't remember how to do that stuff. Have you looked to make sure that you are doing all the steps and using the right numbers? </p>
<p>Before you go off memorizing all of their stuff, on some of the deals they round things off when you aren't supposed to. You also need to realize that a Chem I class doesn't cover the whole book.</p>
<p>You really shouldn't be worried about understanding every single problem. While I understand that you are nervous about taking chemistry, you need to calm down. The point of going to class is to learn stuff. If you already know how to do everything you will be bored out of your mind. I recommend that you put the book aside and enjoy your summer.</p>
<p>.05 mL of water is .05 grams, times 1/(10^10) which is .1ppb, = 5 * (10^-12) grams of CHCl3.</p>
<p>Then, 5 * (10^-12) g divided by the molecular weight of CHCL3, ~119.5 g/mol, gets 4.184 * (10 ^-14) mols of CHCl3, which times 6.022 * (10^23) is
~2.5 * (10^10) molecules of CHCl3.</p>
<p>Also beware that those books occasionally have errors in them. If you can't figure out why you're wrong, try a similar problem and see if you do it right. If you do, odds are they made a mistake.</p>
<p>Oh I used that book the summer before first year. I didn't find it all that helpful.
What I recommend you do is see what book they used last year and go from there.
The reason why this book was not helpful is that they seem to skim alot and not go as in depth. However it was a good groundwork.
It was better for cal. then chem though, you plan on taking that which I'm assuming you are GET THAT ONE ALSO!</p>