A. RbOH -------> Rb+ + OH-
      Â
0.125MÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0.125M
   [OH-]   = [RbOH]
  [OH-]  = 0.125M
  POH  = -log0.125
              Â
= 0.9030
PHÂ Â Â = 14-POH
          =
14-0.9030Â Â = 13.097
  HCl + RbOH --------> RbCl + H2O
no of moles of HCl = no of moles of RbOH
 Â
M1V1Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
= M2V2
0.11*V1Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
= 0.125*23.4
       Â
V1Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
= 0.125*23.4/0.11Â Â Â = 26.6ml
  M  = MBVB -MAVA/VA+VB
          =
0.125*23.4-0.11*5/23.4+5
          =
2.375/28.4Â Â = 0.084M
[OH-] = M = 0.084M
POHÂ Â = -log[OH-]
          Â
= -log0.084Â Â = 1.0757
PHÂ Â Â = 14-POH
        =
14-1.0757Â Â = 12.9243
D. MÂ Â = MAVA -MBVB/VA+VB
         Â
=0.11*26.6- 0.125*23.4/23.4+26.6
          =
0.001/50Â Â = 0.00002M
     [H+] = M = 0.00002M
    PH = -log0.00002
           Â
= 4.6989