CHM 130 Spring 2007 Diebolt              Take Home Quiz 5. Key

 

1)    A 25.8 L sample of gas has a pressure of 695 torr at 17 °C.  What is the volume if the pressure is changed to 1.85 atm and temperature to 72 °C? (5 pts)

            T1 = 17 + 273 = 290 K                 V1 = 25.8 L

            T2 = 72 + 273 = 345 K          P2 = 1.85 atm                                    V2 = ?                                    

                                        Solve for V2:   

                                       = 15.2 L            

2)    A sample of gas occupies 1.13 L at STP.  What is the pressure (atm) of this gas if it occupies 725 mL at 65 °C?  (5 pts)

            V1 = 1.13 L                                         STP: T1 = 273 K                     P1 = 1 atm

                   T2 = 65 + 273 = 338 K          P2 = ?

                                        Solve for P2:  

                                                  =   1.93 L

 

3)    Calculate the mass percent concentration of a MgCl2 solution prepared by dissolving 25.0 g of MgCl2 in 525 g of water.  (5 pts)

 = 4.55 %

 

4)    What mass of water is required to dissolve 12.5 g of NaCl during the preparation of a 7.25% NaCl solution? (5 pts)

           = 160. g water

 

5)    Calculate the molarity of a K2SO4 solution prepared by dissolving 65.5 g of K2SO4 in 575 mL of solution. (5 pts)

 

 

= 0.654 M K2SO4