A diver breathes a heliox mixture with an oxygen mole fraction of 0.050. What must the total pressure (in atm) be for the partial pressure of oxygen to be 0.21 atm?

About 3% of the water on earth is freshest. only about 40% of that freshwater is available for human use. why is so much freshwater unavailable for human use?

What two factors can affect the properties of a hydrocarbon? a. the number of its carbon atoms and the number of single bonds b. the number of its carbon atoms and the arrangement of its atoms c. the arrangement of its atoms and the number of its double bonds

Why must humans find substitutes for many minerals found on earth? (a) form at an extremely slow rate (b) controlled by other countries (c) too deep in the earth to collect