Question

3. How many grams of oxygen are collected in a reaction where 235ml of oxygen gas is collected over water at temp of 25 C and a total pressure of 697 torr

4. a 3.22 g sample of zinc reacts with phosphoric acid to produce hydorgen gas. Find the volume of gas in liters, produced at 766 torr and 25 C

Answer 1

Ans 3.

Since the gas collected over water it is not pur.using standerd table for vapore preeser at different tempreture,the vapore pressere of water at 25 0c is 23.8 torr
Totale pressere =697 torr
Volume of the gas collectd, V= 235 ml
                                                           = 235ml*1L/1000ml
                                                            =0.235 L
Tempreture of the gas isT= (25+273)K
                                                    = 298K

Partial pressere of oxygen gas P = Ptotal+PH2o
                                                                                                      = 697 - 23.8
                                                                    = 673.2 torr
                                                                     = 673.2*1 atm/760 torr
                                                                     = .886 atm
                                                  Using idial gas law
                                                                Pv=nRT
                                                              n = PV/RT
     Mole for oxygen gas,no2 = ( 0.886*0.235)/(.0821*298)
                                                                     = 8.51 * 10^-3 moles.
       Then ,
      Mass of oxygen gas = No moles oxygen gas *Molar mass
                                            = 8.51 * 10^-3 (32.0/1)
                                            = 0.272 g.