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Strong Acid Strong Base Titrations

 

The titration of 50.0mL of 0.150M HCl with 0.150M NaOH is carried out in a chemistry laboratory. Calculate the pH of the solution after these volumes of the titrant have been added. Use these results to plot the titration curve.

   pH

Vol. NaOH

 

0.0mL    

 

25.0mL

 

49.9mL

 

50.0mL

 

50.1mL

 

75.0ml

 

 

 

0.0ml of NaOH            50.0mL 0.150M HCl

pH=-log0.150M

pH= 0.82

 

25.0ml of NaOH to 50.0mL of HCl

Moles H+=50.0mL x 0.150M=7.50mmol

Moles OH-=25.0mL x 0.150M=3.75mmol

 

 

H+  + 

OH- 

  H2O

I

7.50mmol

3.75mmol

 
C -3.75mmol -3.75mmol  
E 3.75mmol 0  

                                     

  [H+]= 3.75mmol =0.05M
25.0mL +50.0mL

pH=-log[H+]

pH=-log[0.05M]=0.82

 

49.9ml of NaOH to 50.0mL of HCl

Moles H+=50.0mL x 0.150M=7.50mmol

Moles OH-=49.9mL x 0.150M=7.485mmol

 

 

H+  + 

OH- 

  H2O

I

7.50mmol

7.485mmol

 
C -7.485mmol -7.485mmol  
E 0.015mmol 0  

                                     

  [H+]= 0.015mmol =0.000 15M
49.9mL +50.0mL

pH=-log[H+]

pH=-log[0.000 15M]=3.82

 

50.0ml of NaOH to 50.0mL of HCl

Moles H+=50.0mL x 0.150M=7.50mmol

Moles OH-=50.0mL x 0.150M=7.50mmol

 

 

H+  + 

OH- 

  H2O

I

7.50mmol

7.50mmol

 
C -7.50mmol -7.50mmol  
E 0 0  

neutralization  pH=7

 

50.1ml of NaOH to 50.0mL of HCl

Moles H+=50.0mL x 0.150M=7.50mmol

Moles OH-=50.1mL x 0.150M=7.515mmol

 

 

H+  + 

OH-

  H2O

I

7.50mmol

7.515mmol

 
C -7.50mmol -7.50mmol  
E 0 0.015mmol  

                                     

  [OH- ]= 0.015mmol =0.000 15M
50.1mL +50.0mL

pOH=-log[OH-]

pOH=-log[0.000 15M]=3.82

pH=14-3.82=10.18

 

75.0ml of NaOH to 50.0mL of HCl

Moles H+=50.0mL x 0.150M=7.50mmol

Moles OH-=75.0mL x 0.150M=11.25mmol

 

 

H+  + 

OH-

  H2O

I

7.50mmol

11.25mmol

 
C -7.50mmol -7.50mmol  
E 0 3.75mmol  

                                     

  [OH- ]= 3.75mmol =0.030M
75.0mL +50.0mL

pOH=-log[OH-]

pOH=-log[0.030M]=1.52

pH=14-1.52=12.48

 

   pH

Vol. NaOH

 0.82

0.0mL    

 1.30

25.0mL

 3.82

49.9mL

 7.00

50.0mL

 10.18

50.1mL

 12.48

75.0ml

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