Chemistry/math problem quick help :D

audiobliss

Ok, I'm trying to figure out a problem for a friend here. This is the problem:

A copper refiner produces a copper ingot weighing 2.39 kg. If the copper is drawn out into a wire of diameter 1.400 mm, how many feet of copper wire can be obtained from the ingot? (The density of copper is 8.94 g/cm3, Volwire = pr2l.)

I personally haven't ever done a problem like this, but it seems pretty straight-forward. This is how I'm inclined to do it: (I don't feel like typing all this again, so I've pasted in how I tried to explain earlier how I *think* you can do it:

Ok, well. The only thing we know about this wire that we want to make is that its diameter is 1.400mm. So, we're going to have to use volumes to figure this out (as far as I can tell). We can convert 2.39kg into grams and use 8.94g/cm^3 to figure out the volume of copper that we have in cm^3. Then we can convert that to mm^3 to work with the cylinder. Once we have that, we can use the formula for the volume of a cylinder (the wire) to find out how long it is. How? Because we know two of the variables: volume (the answer), and the diammeter. We can plug those two values into the formula for the volume of a cylinder, and find out the height, or the length of the wire.

Doing it like this we have: 2.39kg x 100 = 2390g. 2390g (divided by) 8.94g = 267.3378076cm^3 of copper. Now we convert to mm^3: 267.3378076 x 1000 = 267337.8076mm^3. We can now plug this into the formula for the are of a cylinder to find the height of the cylinder and thus the length of the wire. V = base x height. Base: A = pi(r)^2. A = pi(.7)^2 = 1.5393804. So, now we have 267337.8076 = 1.5393804 x h. We divide by 1.5393804 and get h = 173665.8512mm.

So, our wire should be 173665.8512mm long. Since we're asked for feet (thanks bobman1235!!), divide this by 10 to get cm, then divide by 2.54 to get inches, then divide by 12 to get feet. I'm sure there's a more direct way to do that, but I don't know it. This gives us 569.769853 feet.

Now, I don't know if I did that right. I have no idea what the 'Volwire = pr2l' means, so I'm suspecting I did something wrong. If you can help me out with this, I'd really appreciate it!

Thanks!

MacLeod

Show off.

audiobliss

MacLeod wrote:

Show off.

Since I'm asking for help...I don't really feel like a show off....but hey, if I am.....cool!!



Oh, and thanks for the help!

MacLeod

Glad to be of service!

The fact that you actually know what all that means shows youre a lot smarter than me! I guess Im just jealous!

audiobliss

MacLeod wrote:

The fact that you actually know what all that means

I said I don't know what the 'pr2l' means....lol

MacLeod wrote:

shows youre a lot smarter than me!

Has nothing to do with smarts. Just means I've learned about it.

However, trying to build a 'box' with 4 sides does have do to with smarts!

bobman1235

pr2l is supposed to be (pi)r(squared) times length... which si what you correctly assumed.

They kinda trick you in the question by asking how many FEET you get, so convert your mm to feet (just type it into google...).

Pretty close though

(edit : just realized i corrected something you didn't even do wrong... i'm an ****)

MacLeod

audiobliss wrote:

However, trying to build a 'box' with 4 sides does have do to with smarts!

You better believe it! Not just anybody could pull that off!

audiobliss

Thanks bobman1235. Yeah, another friend pointed out my problem with the mm^3 (and told me what the 'pr2l' was supposed to be). I hate it when they give you those formulas when you should be more than able to figure it out yourself. I mean, I've never done a problem like that, and I figured it out.

I fixed the mm^3 in the quote above. Hmm. I hadn't seen the feet at all, lol! I'll see if I can't convert it.

Thanks!

audiobliss

bobman1235 - ROFL Yeah, I did have it wrong, but I corrected it for reference.

Shizelbs

Sorry if I wrong, or if it was just a typo, but the factor for converting inches to centimeters is 2.54, not 2.94.

audiobliss

Shizelbs wrote:

Sorry if I wrong, or if it was just a typo, but the factor for converting inches to centimeters is 2.54, not 2.94.

Thanks, shizelbs! That's where I'm wrong! My answer wasn't quite adding up! I bet that's it! Man, it's been a long time since I've worked with these conversions!

Thanks!

Polkersince85

1.0" = 1.0 / .03937 =25.4000508 mm / 10 = 2.54000508 cm

1.0' = 1.0 x 12 = 12 / .03937 = 304.8006096 mm

audiobliss

Where are you getting the '.03937' from?

petrym

I got 64.004764258729 meters, which converts to 209.989390771 feet. Round it up to 210 feet and call it good!

All unit conversions handled internally by TI-89 calculator.
My calcs: 1st get the volume of the sphere (2.39 kg) / ((8.49 gm/cm^3)) = .000282507656m^3

solve for the radius of the sphere: v=pi r^2 l = .040656863076m

solve for the length of cylinder by pi ^2 h(height or length in this case) since the volume remains the same = l = Vol/(pi r^2) = 64.004764258729 meters

beardog03

my brain hurts...!!








hey,whats that liquid stuff running out of my ears..?!!

cfrizz

beardog03 wrote:

my brain hurts...!!








hey,whats that liquid stuff running out of my ears..?!!

AMEN!!

2 mind numbing threads so far!!!! What is there a full moon out tonight or what? :eek:

Ron-P

Hey, don't forget the +1

Mike682

That's why I love stats.....most gets calculated on the computer..I couldn't imagine inverting a matrix by hand...

CrBoy

I used know all this Chemistry stuff but I forgot pretty much everything I knew on this subject... I feel stupid now...

billbillw

CrBoy wrote:

I used know all this Chemistry stuff but I forgot pretty much everything I knew on this subject... I feel stupid now...

There is really no chemistry involved in this problem.
It is purely geometry calculations, a little physical science (density), and basic unit conversion.

CrBoy

billbillw wrote:

There is really no chemistry involved in this problem.
It is purely geometry calculations, a little physical science (density), and basic unit conversion.

sure... I based my comment only in the thread name... not in the actual content of the posts

Polkersince85

audiobliss wrote:

Where are you getting the '.03937' from?

A meter is 39.37 inches. a mm is 1/1000th of a meter.
Divide inches by .03937 to get mm.
Multiply mm by .03937 to get inches
Just an accurate conversion factor to remember IMO

aaharvel

math is almost as bad as learning a foreign language. I feel your pain.

petrym

I made an oops in my original equations of making the radius of the wire as 1.4mm versus the actual value of 1/2 diameter of .7

That makes the revised length as 128.009528517 meters = 419.978781541 feet or about 420 feet.

audiobliss, did you ever get the proper answer from your friends work?

audiobliss

No, I didn't. I should ask her to see who's right; we have three answers now, I believe! lol