Chem11TEST

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Unit VII.4: Stoichiometry in Excess Quantities By Stephani R., Kevin T., and Nancy W. Chemistry 11, Block F(D1P2)

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These are the characters that are going to help us learn the concept of excess quantities in Stoichiometry. :D ?Cammy(C)? ?Vicki(V)? ?Damien(D)?

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V: Guys, we've got a big problem. D: Whaddaya mean? V: Someone messed up the inventory.

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C: They WHAT?! Who was handling that?! D: Um... that might've been me... C: You are so dead... V: Well, we can still put some together. We've got... 250 discs, 300 cases, 300 labels, and 400 liners.

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C: -sigh- Dude, how'd you mess it up so much? V: I guess I put the wrong numbers in...

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C: -sudden realization- D: You've got that look on your face again...

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C: This is totally like chem class. D: But there are no mall- mell-

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C: Moles? D: Yeah, those things. Or any chemicals or stuff. C: ...weren't you paying attention last week? D: Well... I think I was sleeping.

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C: -horrified look- You were sleeping through stoichiometry?! V: Stoichi- what? D: My thoughts exactly.

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C: -sigh- Stoichiometry goes something like this: You need certain amounts of everything when you're reacting chemicals. For example, you need 2 moles H2 and 1 mol O2 to make 2 moles of H2O. V: Wait, what? C: Hydrogen and oxygen come in pairs. To make water, A.K.A. “H2O”, you need two pairs of hydrogen and one pair of oxygen to make one unit of water. V: I still don't- C: Just pretend you understand. Now, let's pretend everything in our inventory is a chemical. We have 250 discs, 300 cases, 300 labels, and 400 liners. How many CDs can we make? D: Well...

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C: Never mind what you think. We're going to use a little thing called “excess stoichiometry”. It's where you can only make a limited amount of a particular substance cause you only have a limited amount of one of the reactants... or, you could say, ingredients. D: Why wouldn't you just use the right amount? C: Sometimes it's like our situation where you don't have enough. Sometimes it's dangerous to leave something unreacted; other times it's because it's a really expensive chemical. Now be quiet and let me explain. C: The amount of something you can make depends on which reactant has the least amount of moles. Let's pretend that every piece we need is one mole. How many CDs can we make if we have 250 discs, 300 cases, 300 labels, and 400 liners?

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D: Well, the smallest amount is 250, so... 250? C: Not quite. You have to remember: These things always need to be balanced. We need one disc, one case, one label, and two liners per CD. So, how many “moles” of liners do we actually have with 400 total? D: Um... 400 divided by 2... 200?

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C: Exactly! So, what's our smallest amount? D: 200. C: So how many CDs can we make? D: 200! C: You've finally got it! Now, where is everything?

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D: Well... I kinda... forgot. C: -death glare-

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This is the end of our presentation. Thanks for watching!!