1.) A rigid and sealed cylinder contains 0.250 mol of helium gas, 0.500 mol of neon gas, and 0.150 mol of nitrogen gas. The total pressure inside the cylinder is 9.0 atm. Helium has a partial pressure of:

A: 0.250 atm

B: 0.300 atm

C: 3.00 atm

D: 2.50 atm

E: 5.00 atm

2.) How many moles of oxygen gas are needed to produce 67.2 L of H2O (g) at STP in the presence of excess hydrogen?

2H2 (g) + O2 (g) = 2H2O (g)

A: 3.0 mole

B: 6.0 mole

C: 1.5 mole

D: 1.0 mole

E: 4.0 mole

3.) A gaseous solution contains 0.40 mol Ar, 1.20 mol He, and 0.40 mol Ne. What is the mole fraction of He in the mixture?

A: 0.120

B: 1.20

C: 0.333

D: 0.60

E: 0.80

4.) A chemist places 2.5 moles of Cl2 (g) and 2.0 moles of HI (g) in a sealed 2.0 L vessel where the following reaction goes to completion at 25 C:

2HI (g) + Cl2 (g) = 2HCl (g) + I2 (s)

Which of the following substitutions will give the value for the total pressure in the cylinder?

A: [(3.5)(0.0821)(298)]/2.0

B: [(4.5)(0.0821)(298)]/2.0

C: [(4.5)(0.0821)(25)]/2.0

D: [(3.5)(8.314)(298)]/2.0

E: [(2.0)(0.0821)(298)]/2.0