Exam Review s2

[00:00:01]Well, it's that time of year, exam review time.

[00:00:05]Um, please do this on a separate piece of paper just because you want to make sure you still have these papers. Um, I should be able to get all your graded papers back to you uh, in a timely manner.

[00:00:17]But, if you have this copy, you'll know kind of things that are going on. So, let's review a couple of these and then you're going to be on your own. This is meant to be a short video.

[00:00:25]Uh, just a reminder.

[00:00:27]So, here we go. We got 40 g of uh, sodium N A N 3 40 g and they want that to be moles. Well, that's periodic table time.

[00:00:44]And we know what you have goes on the bottom.

[00:00:48]And what you want goes on top.

[00:00:53]When we go to the periodic table, we will add up the sodium, which is 23, and then we will add uh, the nitrogen three times.

[00:01:07]And the answer is 65 g. So, when we do this math, it's going to be this 40 times 1 divided by 65.

[00:01:19]And we'll get an answer. So, 40 divided by 65. So,.615.

[00:01:30]And of course, that'll be moles.

[00:01:32]Okay?

[00:01:34]Uh, down here, the next one, we say, "Hey, calculate the grams of each." So, now it's the other way around. They give you moles, so let's take a look at this one.

[00:01:45]1.6 moles barium chloride.

[00:01:53]Okay? And we know in this situation, we're going to have moles on the bottom, grams on top.

[00:02:05]Because we're getting information from the periodic table, we know that it's 1 mole, so 1 mole. Um give me a second here. Let me look up barium.

[00:02:19]Barium is 137.3.

[00:02:22]So, this is 137.

[00:02:26]3 and two of these is actually 71.

[00:02:29]So, this is total is going to be 2 108.3 g.

[00:02:36]All right, let's do the math on that.

[00:02:37]So, we'll do the same process. What do you mean by the same process? We're going to take this 1.6 and multiply it times this top number, and then divide by the one.

[00:02:48]So, 1.6 * 2 uh 08.3, and we get 330 uh 33. And that would be fine to put as grams of barium chloride.

[00:03:06]Another example down here, combustion.

[00:03:09]Uh writing the combustion reactions is uh important. It's one of the five types of reactions that you need to know. You need to know single replacement, double, synthesis, decomposition.

[00:03:22]Those are the ones you have to know.

[00:03:24]Okay. Oops, sorry.

[00:03:26]Not that.

[00:03:28]Undo, undo. 12.

[00:03:30]plus oxygen.

[00:03:33]Because they said combustion, we are always going to make carbon dioxide and water.

[00:03:41]Um also, we are only allowed to put numbers in this position when we go to balance.

[00:03:47]Start with the most complex, and s- and with your simplest, which is this oxygen.

[00:03:55]So, five carbons on this side. If I put a five here, I will have five carbons on on the other side. There are 12 hydrogens. So, if I put a six here, I will have 12 hydrogens. So, in essence, the C5H12 is handled.

[00:04:11]We have to do a check.

[00:04:13]Over here, I'm going to have 10 oxygens cuz 5 * 2.

[00:04:18]And then I also have six more over here for a total of 16. The only number that will balance this now is right here.

[00:04:28]To put an eight there. So, the numbers would be one. Sorry, that doesn't look like a one. Let me go back.

[00:04:38]One to to eight to five to six. All right, let's keep moving.

[00:04:48]Types of reactions, yeah, that was said I just mentioned. So, if you go back and get those types down, please put it on another piece of paper.

[00:04:56]Um this is never goes away. We must um it's the conservation of energy. We can't create nor destroy.

[00:05:19]Matter. So, we have to have the same amount of matter on both sides.

[00:05:23]We go for these graphs. I want you to look through the gas chapters, and this is you know, pressure versus volume.

[00:05:30]We knew that was an inverse relationship, so it looks like this.

[00:05:35]Uh pressure and temperature, go look it up.

[00:05:37]This also standard temperature and why we use Kelvin is pretty straightforward to look up in the book in the gas chapter.