Ch. 13 gas                                70 points                                                          chemistry

Show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of significant figures in your answer.  You may use mathematica to do the “tedious” algebra.

1.  A 3.0 L container at 325 K has 4.0 grams H2, 16.0 grams O2, and 14.0 grams N2.  [20 points; weekly quiz problem]

a. what is the number of moles of each gas ?

b. what is the mole fraction of N2 ?

c. what is the partial pressure of N2 ?

d.  what is the total pressure ?

2.  A 25 mL syringe has a pressure of 750 torr at 25 ºC.  The syringe’s volume was changed to 35 mL and the temperature changed to 37 ºC; what is the new pressure in the syringe ?  Assume the number of moles of gas did not change.  [10 points; weekly quiz problem]

3. Solve  [15 points; similar to HW problem 13.4 & 13.5]

a. 752 mm Hg =  __ atm

b. 2.7 atm =  __ kPa

c. 225 kPa  =  __ torr

4.  85 mg of a (hypothetical) gas has a volume of 125 mL at 85 ºC and 745 mm Hg; what is the molar mass of the gas ?  [10 points; similar to HW 10.37]

5.  In regards to the combustion of propane

C3H8  +  O2 →   CO2  +  H2O

What is the minimum volume of oxygen gas at 25 ºC and 1.04 atm for the complete combustion of 5.53 grams of propane ?  [15 points; HW 13.47]