Four gases were combined in a gas cylinder with these partial pressures: 3.5 atm n2, 2.8 atm o2, 0.25 atm ar, and 0.15 atm he.
what is the total pressure inside the cylinder? 6.7 atm
what is the mole fraction of n2 in the mixture? 0.52 atm

2 equations: first, p subscript t equals p subscript 1 plus p subscript 2 plus p subscript 3 plus ellipses plus p subscript n. second: startfraction p subscript a over p subscript t endfraction equals startfraction n subscript a over n subscript t endfraction.
what is the mole fraction of o2 in the mixture? atm
what is the mole fraction of ar in the mixture? atm

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

The density of the solid phase of a substance is 0.90 g/cm3 and the density of the liquid phase is 1.0 g/cm3. a large increase in pressure will a. lower the freezing point b. raise the freezing point c. lower the boiling point d. raise the triple point e. lower the triple point

1.) which of the following is a molecule but not a compound? a.he b.f2 c.h2o d.ch4 2.) what is a physical combination of substances? a.a compound b.a molecule c.a mixture d.an element 3.) what is a chemical combination of substances? a.a compound b.an atom c.a mixture d.an element 4.) what is the relationship between the solute and solvent in a solution? a.they form a compound b.they form a mixture c.they form molecules d.they form chemical bonds 5.) the gases in air dissolve in water. what would be one way to reduce the amount of a gas dissolved in water? a.add more water b.reduce the air pressure c.increase the air pressure d.stir the water 6.) how would you determine the solubility of a substance? a.find how well it dissolved various substances. b.find the mass and the volume of the substance. c.find the temperature at which the substance evaporated. d.find how much i was able to dissolve in a solute. 7.) the periodic table organizes all of the kinds of a.molecules. b.compounds. c.atoms. d.ions. 8.)what distinguishes two substances combined to become a compound vs. two substances combined to become a mixture? a.whether they can be easily separated b.whether they chemically bond together c.whether they both are visible d.whether they are heterogeneous 9.) the principle components of air are: n2 78% o2 21% ar 0.95% co2 0.038% this is a solution of a.molecules and atoms. b.molecules. c.compounds and molecules. d.atoms.