The Bends Scuba Diving

the bends scuba diving
chemistry helppppppp pleaseeeeeee?

1. the heat of fusion for thallium is 21 J/g and its heat of vaporization is 795 J/g. Thallium's melting point is 304 degrees C, and its boiling point is 1457 degrees C. the specific heat of liquid thallium is 0.13 J/g(degree C). How much heat is needed to change 236 g of solid thallium at 304 degrees C to vapor at 1457 degree C and 1 atm?

2. mixtures of helium and oxygen can be used in scuba diving tanks to help prevent "the bends". for a particular dive, 46L of He and 12L of oxygen, both at 25 degrees C and 760 torr, were pumped into a tank with a volume of 5L. calculate the partial pressure of each gas and the total pressure in the tank at 25 degrees C.

3. calculate the amount of heat in kilojoules released when 50 grams of steam at125 degrees C are converted to 50 grams of ice at -125 degrees C

pleaseeeeeeeeeeeeeeeeeeeeee helppppp me someone and if you could show work so i can follow along and teach myself

3. calculate the amount of heat in kilojoules released when 50 grams of steam at125 degrees C are converted to 50 grams of ice at -125 degrees C

There are five calculations to be done:

1) cool steam from 125 to 100
2) condense steam at 100
3) cool liquid from 100 to 0
4) freeze water at 0
5) cool water from 0 to 125

I do a problem like this, but going from ice to steam. It's here:

http://www.chemteam.info/Thermochem/Time-Temperature-Graph.html

At this link:

http://www.chemteam.info/Thermochem/Thermochem-Example-Probs3.html

starting at problem #4, there are some other problems which use five equations to solve.

For your problem one, you need three equations:

1) melt thallum at 304
2) heat thallium from 304 to 1457
3) boil thallium at 1457

Here are the set up without units:

1) (21)(236)
2) (236)(1153)(0.13)
3) (795)(236)