Ch.  9 & 13  stoichiometry & gas                                test [100 points]                                              honors Chem

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. 

1. fill-in the blank; use the lowest ratio of integers; if it’s “1”, then enter “1”.  [15 points]

a. ___ C5H12  +  ___ O2  -->  ___ CO2  +  ___ H2O

b. ___  Co(NO3)2  +  ___  (NH4)2S  -->  ___  Co2S3  +  ___  NH4NO3

c. Ammonium chloride reacts with lead (II) nitrate to form . . . :  _____________________________________

 

2.  fill-in the blank.  [15 points]

a. 1.5 atm  =  ___ kPa

b. 755 torr  =  ____  atm

c. 125 kPa  =  ___  mm Hg

 

3. A 65.0 mL syringe has a pressure of 95.0 kPa and the room temperature is 21.0 ºC.  The syringe’s volume was reduced to 25.0 mL and it was put into a freezer at -5.0 ºC; what is the pressure in the syringe ?   [10 points]

 

4.  At STP, 2.0 L N2 reacts with 5.0 L H2 to form 0.11 moles NH3; what is the % yield in the reaction ?  [20 points]

 

5. Mixing aqueous solutions containing 125.0 g calcium nitrate and 125.0 g sodium phosphate forms a precipitate.  Assume the reaction has a 85 % yield; what is the mass of the precipitate in the reaction ?  [25 points]


6. A 5.0 L container has 4.0 g hydrogen gas, 10.0 g helium gas, and 42.0 g nitrogen gas.  The temperature in the container is 37.0 ºC.    [15 points]

a.  What is the total pressure ?

b.  What is the partial pressure of nitrogen ?

c. What is the mole fraction of helium ?