Question

A 50.0 mL solution of 0.178 M KOH is titrated with 0.356 M HCl. Calculate the pH of the solution after the addition of each of the given amounts of HCL. 0.00 mL pH = 6.00 mL pH = 12.5 mL pH = 18.0 mL pH = 24.0 mL pH 24.0 mL pH = 25.0 mL 25.0 mł pH=C pH = 26.0 mL pH = 31.0 mL pH =

Answer 1

KOH(aq) ---------> K^+ (aq) + OH^- (aq)
0.178M------------------------0.178M
[OH^-] = [KOH] = 0.178M
POH = -log[OH^-]
     =-log0.178
     = 0.7496
PH = 14-POH
     = 14-0.7496
      = 13.25
KOH---------------- HCl
MB = 0.178M----- MA = 0.356M
VB = 50ml ---------VA = 6ml
   M = MBVB-MAVA/VA+ VB          MBVB>MAVA
      = 0.178*50-0.356*6/(50+6)
      = 6.764/56
       = 0.1208M
[OH^-] = M = 0.1208
POH = -log[OH^-]
     =-log0.1208
     = 0.918
PH = 14-POH
     = 14-0.918
      = 13.082
12.5ml
KOH---------------- HCl
MB = 0.178M----- MA = 0.356M
VB = 50ml ---------VA = 12.5ml
   M = MBVB-MAVA/VA+ VB          MBVB>MAVA
      = 0.178*50-0.356*12.5/(50+12.5)
      = 4.45/62.5
       = 0.0712M
[OH^-] = M = 0.0712
POH = -log[OH^-]
     =-log0.0712
     = 1.1475
PH = 14-POH
     = 14-1.1475
      = 12.8525
18ml
KOH---------------- HCl
MB = 0.178M----- MA = 0.356M
VB = 50ml ---------VA = 18ml
   M = MBVB-MAVA/VA+ VB          MBVB>MAVA
      = 0.178*50-0.356*18/(50+18)
      = 2.492/68
       = 0.0366M
[OH^-] = M = 0.0366
POH = -log[OH^-]
     =-log0.0366
     = 1.4365
PH = 14-POH
     = 14-1.4365
      = 12.5635
24ml
KOH---------------- HCl
MB = 0.178M----- MA = 0.356M
VB = 50ml ---------VA = 24ml
   M = MBVB-MAVA/VB+ VA          MBVB>MAVA
      = 0.178*50-0.356*24/(50+24)
      = 0.356/74
       = 0.00481M
[OH^-] = M = 0.00481M
POH = -log[OH^-]
     =-log0.00481
     = 2.3178
PH = 14-POH
     = 14-2.3178
      = 11.6822
25ml
OH---------------- HCl
MB = 0.178M----- MA = 0.356M
VB = 50ml ---------VA = 25ml
   M = MBVB-MAVA/VB+ VA          MBVB>MAVA
      = 0.178*50-0.356*25/(50+25)
      = 0/75
       = 0.0

neutral PH = 7
26ml
HCl ------------------- KOH
MA = 0.356M---------- MB = 0.178M
VA = 26ml-------------MB = 50ml
M = MAVA-MBVB/VA+ VB
   = 0.356*26-0.178*50/(26+50)
   = 0.356/(76)
   = 0.004684
[H^+] = M = 0.004684M
PH = -log[H^+]
    = -log(0.004684)
    = 2.3294
31ml
HCl ------------------- KOH
MA = 0.356M---------- MB = 0.178M
VA = 31ml-------------MB = 50ml
M = MAVA-MBVB/VA+ VB
   = 0.356*31-0.178*50/(31+50)
   = 2.136/(81)
   = 0.02637
[H^+] = M = 0.02637M
PH = -log[H^+]
    = -log(0.02637)
    = 1.5788