Concept explainers
Interpretation:
The pH at the stoichiometric point of the titration of 25.0 mL of 0.010 M HClO(aq) with 0.020 M KOH(aq) has to be calculated.
pH definition:
The concentration of hydrogen ion is measured using pH scale. The acidity of aqueous solution is expressed by pH scale.
The pH of a solution is defined as the negative base -10 logarithm of the hydrogen or hydronium ion concentration.
pH = -log[H3O+]
On rearranging, the concentration of hydrogen ion [H+] can be calculated using pH as follows,
[H+] = 10-pH

Answer to Problem 6H.2AST
The pH at the stoichiometric point of the titration of 25.0 mL of 0.010 M HClO(aq) with 0.020 M KOH(aq) is 9.68.
Explanation of Solution
The initial amount of HClO present in the analyte solution is
n(HClO) = (0.025×10-3L)×(0.01 mol×L-1) = 2.5×10-4 mol = 0.25×10-3 mol = 0.25 mmol
The amount of OH− required to react with HClO is calculated and their reaction stoichiometry is
1 mol OH- = 1 mol HClO.
n(OH-) = (initial amount of HClO in the analyte)×1 mol OH-1 mol HClO = (0.25×10-3 mol)×1 mol OH-1 mol HClO = 0.25 ×10-3 mol = 0.25 mmol
Therefore, the OH− ion required to react with HClO is 0.25 mmol.
From the stoichiometric point the amount of ClO− is equal to the amount of OH− added.
n(ClO-) = 0.25 mmol
The amount of OH− ions present in the volume of titrant is calculated as.
Vadded = OH-ion required to react with HClOconcentration of OH-ion = 0.25×10-3 mol0.020 mol⋅L-1 = 1.25×10-2 L = 12.5 mL
Hence, the amount of OH− ions present in the volume of titrant is 12.5 mL.
The total volume of the solution at the stoichiometric point is calculated as,
Vfinal = Vinitial+Vadded = 25.0+12.5 mL = 37.5 mL
The concentration of ClO− ions at the stoichiometric point is
[ClO-] = amount of ClO- present in the analyte solutiontotal volume of the solution = 0.25×10-3mol3.75×10-2 L = 0.007 mol⋅L-1
Therefore, the concentration of ClO− is 0.007 mol⋅L-1.
The chemical equilibrium reaction is given below.
ClO-(aq)+H2O(l)⇌HClO(aq)+OH-(aq)
Kb=[HClO] [OH-][ClO-]
ClO− | HClO | OH- | |
Initial concentration | 0.007 | 0 | 0 |
Change in concentration | -x | +x | +x |
Equilibrium concentration | 0.007-x | x | x |
The equilibrium concentration values are obtained in the above table and is substituted in above equation and is given below.
Kb=x×x0.007-x
The above equation, assume that the x present in 0.007-x is very small than 0.007 then it can be negligible and it follows,
Kb=x20.007
Hydrochlorous acid Ka value is 3.0×10-8 from this we can calculate the Kb value, is given below.
Ka×Kb=Kw Kb = KwKa = 1.0×10-143.0×10-8 = 3.33×10-7
Therefore, the Kb value of HClO is 3.33×10−7 substitute this in below equation.
Kb=x20.0073.3×10-7= x20.007 x2 = (3.3×10-7)×0.007 x = √(3.3×10-7)×0.007 = 4.81×10-5
Hence, the concentration of OH- is 4.81×10-5.
Now, we can calculate the pH of the solution,
pOH =-log( 4.81×10-5) = 4.32pH+pOH = 14 pH = 14-4.32 = 9.68
Hence, the pH of the solution at the stoichiometric point of the titration of 25.0 mL of 0.010 M HClO(aq) with 0.020 M KOH(aq) is 9.68.
Want to see more full solutions like this?
Chapter 6 Solutions
CHEMICAL PRINCIPLES (LL) W/ACCESS
- Pls help.arrow_forwardPls help.arrow_forward16) A 2.0 L flask containing 2.0 x 10-3 mol H2(g), 3.0 x 10-3 mol Cl2(g), and 4.0 x 10-3 mol HCl(g) at equilibrium. This system is represented by the following chemical equation: H2 (g) + Cl2 (g) → 2HCl(g) Calculate the equilibrium constant for this reaction.arrow_forward
- 7) The pH of a 0.05M solution of HCl(aq) at 25°C is a. 1.3 b. 2.3 c. 3.3 d. 12.7arrow_forward11) The Ksp expression for copper (II) sulfate is: a. [Cu2+][SO4²¯] b. [Cu²+]² [SO4²]² c. [Cu²+]²[SO4²] d. [CuSO4] 12) Which of the following is true about a chemical system in equilibrium? a. All chemical reactions have stopped b. The concentration of reactants is equal to the concertation of products c. The forward and reverse reaction rates become equal d. The system will remain at equilibrium regardless of any external factorsarrow_forward21) Explain the difference between the rate of a reaction and the extent of a reaction. Why are both of these concepts important, if you are a chemical engineer that is trying to develop a process to produce a large volume of a specific type of chemical compound?arrow_forward
- Chemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage LearningPrinciples of Modern ChemistryChemistryISBN:9781305079113Author:David W. Oxtoby, H. Pat Gillis, Laurie J. ButlerPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781337399074Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage Learning
- Chemistry: Principles and PracticeChemistryISBN:9780534420123Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward MercerPublisher:Cengage LearningGeneral Chemistry - Standalone book (MindTap Cour...ChemistryISBN:9781305580343Author:Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; DarrellPublisher:Cengage Learning




