Question

Not math. Chemistry help!

Answer 1

Give me a sec.

Answer 2

Thank you! ive been stumped for the past hour ): @jb1515g

Answer 3

Okay, first things first. Whenever you are dealing with Chemistry math, it helps to put everything into moles. So the first thing you should do is transfer the 94L of O2 and the 134 grams of NO in moles. Can you do that?

Answer 4

yes so far I got
3.84 mol O2 & 3.13 mol NO

Answer 5

im not sure if I did it correctly?

Answer 6

I got the same number for moles of O2 (I hope you used the ideal gas law!) but not for NO. Show me what you did for that one so I can see.

Answer 7

yes i did use the ideal gas law :) ok let me back track and see where i wrote my work..one sec

Answer 8

ok i think i realized what i did is it 4.47 mol NO?

Answer 9

Yes, that is what I have for moles of NO.

Answer 10

nice :)

Answer 11

Perfect. Now that everything is in moles, it's much easier to go forward. Now you have to look at your balanced equation and figure out your mole ratios for "amount of reactant" versus 'amount of expect product." What do you have for those?

Answer 12

ok is it:
2 mol NO2/1 mol O2
& 2 mol NO2/2 mol NO
?

Answer 13

Correct. So which reactant is your limiting reactant?

Answer 14

that would be NO2

Answer 15

That's your product. Your limiting reactant can only be either of the reactants: O2 or NO.

Answer 16

whoops then i mean NO!

Answer 17

Correct. So, now we know our limiting reactant, the rest is just math. Moles of the limiting reactant (in this case, NO) multiplied by the molar ratio (in this case 2/2, or 1, so it's the same) multiplied by the molar mass of NO2. That gives you EXPECTED grams of product.

Answer 18

ok and for the expected grams i got 134g NO2?

Answer 19

I think i got my percent yield but iffy, is it 70%?

Answer 20

Try the NO2 calculation again. That's not what I got.

Answer 21

ok thats where I'm stuck ):

Answer 22

Watch your formula. Remember there are TWO oxygen atoms. Molar mass is the mass of each element in the formula.

Answer 23

ok let me check!

Answer 24

ok i want to say the g NO2 is .0972? :|

Answer 25

waaait

Answer 26

No, not so. How many moles of NO2 does this reaction make?

Answer 27

Go ahead

Answer 28

it makes 2 moles?

Answer 29

No, remember your molar ratio for NO to NO2 was 2/2, or 1/1. So for every mole of NO, it makes one mole of NO2. And how many moles of NO did we have?

Answer 30

we had 4.47 moles of NO

Answer 31

so would this mean i multiply by the molar mass?

Answer 32

to get the grams?

Answer 33

One second, we're getting close, but we're not quite there. If we had 4.47 moles of NO, and the molar ratio for NO/NO2 was 1/1, how many moles of NO2 do we get from 4.47 moles of NO?

Answer 34

4.47?

Answer 35

Correct! So if we have 4.47 molars of NO2, to get to grams, we multiply by the molar mass.

Answer 36

ok ok so thereforeeeee!

Answer 37

what I do is 4.47*(Molar mass of NO2)=206?

Answer 38

Yes!

Answer 39

AHHHH :D

Answer 40

Now, remember, that is your THEORETICAL yield. To find percent yield, like any percent, you take the amount you ACTUALLY GOT and divide it by what you SHOULD HAVE GOT, then multiple by 100. Standard percentage formula.

Answer 41

let me guess next i divide (93.8 g NO2/206)x100=45.5% ?!?!?!?

Answer 42

Yes, that's what I got.

Answer 43

yay! ok that was my last question on this little hw assignment let me submit it and see how we did *fingers crossed*

Answer 44

One thing I noticed was that you took a lot of liberty with rounding in your calculations. You might want to, in the future, keep the decimal to a few places, for added accuracy. Just a suggestion :)

Answer 45

I've always had trouble with rounding :/ confuses me. but guess what our answer was correct! :) Thank you so much

Answer 46

You didn't think I was going to spend all that time just to get a wrong answer, did you? :P Congratulations, you did good. Do you remember what to do though? That's the most important part.

Answer 47

hehe thank you! i do but ok i forget how i got the mol of NO );

Answer 48

oh wait i think i remember!

Answer 49

Grams/molar mass = moles.
Moles * molar mass = grams.

Remember those two formulas, they are the cornerstone of all stoichiometry. It's vital!

Answer 50

aggh yes your right :(

Answer 51

My high school chem teacher gave us a really silly way to remember it, but to this day, 10 years later, it still sticks. To get to moles, like the animal, you have to dig down into the ground, or "divide" the ground. Remember, to get to moles, divide!

Answer 52

thats funny hehe. Ill try to remember that :)

Answer 53

this is my first time taking chemistry and I'm in my second year in college so I'm overwhelmed!

Answer 54

would you mind if helping with this other short problem?

Answer 55

Not at all. Let's see it.

Answer 56

ok i have done this problem twice each time it changes the #'s around so i don't understand why I'm only getting partial credit !

Answer 57

Boyle's Law, right? It's a simple proportion. P1V1 = P2V2.

So just sub in the numbers:

2.8 * 2.9 = 5.5 * V2 (or x or any variable you feel comfortable with)

Then just solve for the unknown.

Answer 58

ok hm idk why i put 2.0 i had something different in my notes maybe it was just my mistake! i did the same formula format so blah ;p

Answer 59

Did you try it again? What did you get?

Answer 60

1.5L, is that correct?

Answer 61

1.48L would be better, but yes, 1.5L is correct :P

Answer 62

hm ok. Its just because i get confused this website is so particular with significant figures. gets me every time

Answer 63

Yeah, you have to be careful about that. Particularly computer programs, like the one you're working on, will be very, VERY specific about what answer it accepts.

Answer 64

YES -_- i got 3 problems partial credit very frustrating

Answer 65

Well, just think, in the world of Chemistry, when things like medicines need to be measured, the different between 1.5 and 1.48 might be enough to kill someone!

Answer 66

i suppose you have a point aha. Chemistry definitely is tricky for me. i appreciate you helping me!

Answer 67

Any time :)