1. When people go scuba diving they take a gas tank full of gases. What gases are contained in the tank? Estimate the weight of gas present in a full scuba tank?
Volume = 11 L
P = 170 atm
2. If I fill a balloon with helium it will float. Why does it float? Estimate the mass of helium in the balloon.
2006-08-12 13:35:38 · 5 answers · asked by RED MIST! 5 in Science & Mathematics ➔ Chemistry
As a matter of fact, there won't be a test...
I'm in an online school and they don't test. You just complete the assignments and get a credit.
2006-08-12 14:04:43 · update #1
1) The gas(es) in a scuba tank depend on how deep the dive is for. For modest depths. compressed air is used. For deep dives, a mixture of 98% helium and 2% oxygen might be used. No doubt there are other mixes too. (Note, breathing abnormal gas mixtures can be very dangerous).
If you assume that compressed air is used, then you can calculate the mass and hence the weight of gas in a tank using the General Gas Equation:
PV = nRT and n = m/MM to give:
PV = (m/MM) x RT
where
P = pressure say 101.3 kPa ie one atmosphere
V = volume = 11 L in this case
n = number of moles = m/MM
m = mass (g)
MM = molar mass = 28.86 gmol^-1 for air (you should show this)
R = Universal Gas Constant = 8.31 JK^-1mol^-1
T = absolute temperature, lets say 25 + 273 = 298K
From the above, you can calculate the mass of air. To then find weight, multiply by g ie
w = mg
where
w = weight (N)
m = mass (g)
g = acceleration due to gravity = 9.81 ms^-2
If you want lbs weight, multiply the mass in kg by 2.2
2) I presume you have seen He balloons so that you know they "float" in air. This is because the combined mass of the balloon AND the He it contains is less than the mass of air displaced by the balloon. To estimate the mass of He in the balloon, use the equations above. You will need to make reasonable estimates of T, P and V of course.
I hope this helps.
2006-08-12 14:41:41 · answer #1 · answered by Auriga 5 · 0⤊ 0⤋
Okay, I'll give you a hint on #2. Equal temp & pressure, gases expand at equal rates. Look at the position of helium on the periodic table compared to oxygen, nitrogen and other gases that make up the atmosphere.
2006-08-12 14:34:13 · answer #2 · answered by Skeff 6 · 0⤊ 0⤋
What do you mean "You just complete the assignments and get a credit"? Sounds like you have other people completing your assignments instead.
Of course, you're right about you getting the credit.
2006-08-12 15:13:59 · answer #3 · answered by genericman1998 5 · 0⤊ 2⤋
Dang dude.... IM not a science Freek. Ask someone who cares!
Don't you see no one answering your question?
2006-08-12 13:41:39 · answer #4 · answered by Simone 2 · 0⤊ 2⤋
quit trying to get someone to do you homework for ya kid...figure it out....there will be a test....
2006-08-12 13:49:36 · answer #5 · answered by Anonymous · 1⤊ 2⤋