Okay so this may seem a little unusual to ask but if i cannot swim, wouldnt it be a good idea to go snorkeling or scuba diving? i would have someone with me who knows how to swim but i would have though it would be easier as you wear you have an oxygen tank on your bank therefore you wouldnt panic causing yourself to drown? or am i wrong in thinking this?

Speaking as a former lifeguard, and SCUBA instructor, I would strongly recommend you learn to swim properly first, before trying either of these two activities. Both require one to be comfortable about being in the water, including getting one’s face wet, which is not the case for most non-swimmers (and even doggy-paddlers are pushing it).

Although no certification is needed to go snorkelling, and wearing a life vest will stop you from sinking, that may not be enough to enable you to enjoy it. And since that is the whole point of any recreational activity, there is little to be gained from doing so, apart from stress (both for you and anyone who goes with you).

This applies to an even greater extent in SCUBA diving, which has a far higher risk index, including factors that non-divers (and even some entry-level divers, in my experience) have difficulty comprehending. Any diver without a supervisional diving qualification (e.g. PADI Divemaster equivalent or better), who would nonetheless take his non-swimmer friend diving, is destined at best for a stressful experience (for both parties) and at worst, a serious accident, with the accompanying guilt and/or lawsuits (or even criminal prosecution, if the accident is fatal).

One of the prerequisites for becoming certified as a scuba diver is being able to swim, and under PADI standards one of the ‘medical contraindications’ (i.e. absolute no-nos) to starting a course is ‘to overcome a fear e.g. of the water’. No professional instructor (professionalism being defined in terms of ability, knowledge, responsibility, and ethics, rather than simply ‘paid’), regardless of agency, would certify a total non-swimmer to dive.

Having said all that, subject to successful tryouts in standing depth first, I have taken non-swimmers for shallow intro-dives (no certifications issued) in sheltered open water. I had to do everything for them except breathe, but that’s OK, because they enjoyed the experience. However, this very much depends on the individual (both diver and instructor).

A) the mole fractions of two gases?
B) their partial pressures?
C) total pressure?

find moles, using molar masses:
1.96 g He @ 4.00 g/mole = 0.49 moles Helium

60.8 g O2 @ 32.0 g/mol = 1.90 moles oxygen

total moles = 2.39 moles
===========================

A) the mole fractions of two gases?

Helium:
0.49 moles Helium / 2.39 total moles = 0.205 helium’s mole fraction

1.90 mole O2 / 2.39 total moles = 0.795 oxygen’s mole fraction
=================================

B) their partial pressures?

first find total pressure:
PV=nRT
P(5.00L) = 2.39 moles (0.08206 Litre-atm / mol-K)(298K)
total pressure = 11.69 atm

B) their partial pressures?
Helium:
11.69 (0.205 helium’s mole fraction) = 2.396 atm Helium
your answer(3sigfigs): 2.40 atm Helium partial pressure

Oxygen:
11.69 – 2.40 = 9.29 atm oxygen
your answer is: 9.29 atm Oxygen partial pressure
===============================
C) total pressure?

your answer(3sigfigs): 11.7 atm

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

People have used compressed air as their breathing medium since the advent of diving in the 1950s. Its main advantage is that it is readily available and relatively inexpensive to compress into cylinders. Nevertheless, air is not the "ideal" breathing mixture for diving. With a concentration of approximately 79% nitrogen, compressed air poses two potential problems for all divers: susceptibility to nitrogen narcosis (a condition resembling alcoholic intoxication) at deeper depths; and decompression sickness (DCS). Both of these can prove fatal to a diver. In an effort to reduce the ill effects of nitrogen on divers, nitrox was developed.

Nitrox is a generic term that can be used to describe any gaseous mixture of nitrogen and oxygen. In the context of technical diving, nitox is a mixture containing more oxygen than air. The two most commonly used nitrogen-oxygen mixtures contain 32% and 36% oxygen by volume. This differs significantly from compressed air, which contains approximately 21% oxygen by volume. While an increase of 12 to 16% oxygen by volume may not seem drastic, it allows divers to significantly extend their bottom time, and decreases their risk of developing DCS.

The term "mixed-gas diving" refers to any activity in which the diver breathes a mixture other than air or nitrox. The main incentive to dive with "non-air" gas mixtures is to avoid nitrogen narcosis. One type of mixed gas diving involves the use of heliox. This (helium 79% and oxygen 21%) mixture is often used for very deep diving. Unlike nitrogen, helium is not known to have an intoxicating effect at any depth; it has a lower density than nitrogen, making it easier to breathe; and in cases of extended submersion, it improves decompression.

Since there are verious compositions, I will solve the problem for taking helox as basis, that is (helium 79% and oxygen 21%) mixture.

In your question there is no information about the temperature. Therefore I will assume it constant.

To estimate the weight (mass) of the gas mixture in the tube, we have to know the total moles of the mixture. For this we can use the STP conditions to compare (represented by the subscript 1)
P1 = 1 atm
V1 = 22.4 L
n = 1 mol
T = 0°C = 273 K

Tube conditions (represented by the subscript 2)
P1 = 170 atm
V1 = 11 L
n = ? mol
T = 0°C = 273 K

P1V1 / n1T1 = P2V2 / n2T2 (cancel T1 and T2)

(1)(22.4) / 1 = (170)(11) / n2

n2 = 1870 / 22.4 = 83.5 mol

For gases volume percentages = mole percentages
Mole of He = 83.5 x 79/100 = 66.0 mol
Mole of O2 = 83.5 x 21/100 = 17.5 mol
———————————————————
TOTAL : ……………………………… 83.5 mol

Molar mass of He = 4 g/mol
Molar mass of O2 = 32 g/mol

Mass of He = 66.0 mol x 4 g/mol = 264 g
Mass of O2 = 17.5 mol x 32 g/mol = 560 g

Total mass = 824 g

In your first class, called Open Water, you will need what the industry calls "personal gear." Some shops rent everything, but most will require you to buy your personal gear. This includes mask, snorkel, fins and boots.

Everything else can be rented.

Now, to be fully decked out, ready to dive, you need the following items:

1. mask
2. snorkel (some consider this optional)
3. regulator set (1st stage and two second stages, pressure gauge, low pressure hose for BCD)
4. buoyancy control device (BCD)
5. tank
6. weight
7. boots
8. fins
9. exposure protection (ex. wetsuit)
10. depth gauge
11. timing device

If you’re going to own everything, it’s a average min. $1000 investment. Now, if you like high end gear, the min. cost can easily exceed $1000. If you’re really good buying used (great to have friends who dive), then you might be able to get into the sport for less.

Remember, certification first

Assuming you do want to do this professionally, here’s the plan of action I’d recommend:
–Start volunteering at SeaWorld. I’m sure it’s very competitive, but it doesn’t hurt to try. There might be other places nearby where animals are being kept–try volunteering there to build up your resume.
–If you’re not in college yet, apply to a top research institution and get a BA or BS in Biology, Comparative Development, Engineering, Statistics, Chemistry, or Mathematics. Some of those might sound surprising, but they will make you an in-demand person in the field (trust me!).
–While in college, do research with the leaders of the field at your school. In science, doing research is even more important than the grades you get in your classes.
–Every spring, apply for a competitive internship at a zoo, such as this one:
http://www.brookfieldzoo.org/pagegen/pretemp2.asp?pageid=206&template=2&title=Internships&bgtype=BgColor&bg=white&uni=0&motifid=2000002&form=0&nsection=&nlinkid=&anchor=

It’ll be tough, but follow this plan and you’ll be swimming with dolphins in no time. Best of luck!