Textbook Question
What is the pH and the principal source of H3O+ ions in 1.0 * 10-10 M HCl? (Hint: The pH of an acid solution can’t exceed 7.) What is the pH of 1.0 * 10-7 M HCl?
Ch.16 - Aqueous Equilibria: Acids & Bases
Chapter 16, Problem 17-143a
A 100.0 mL sample of a solution that is 0.100 M in HCl and 0.100 M in HCN is titrated with 0.100 M NaOH. Calculate the pH after the addition of the following volumes of NaOH:
(a) 0.0 mL
Verified step by step guidance1
Step 1: Identify the species present in the solution before the titration begins. In this case, we have HCl, a strong acid, and HCN, a weak acid. The strong acid will completely ionize, while the weak acid will partially ionize.
Step 2: Calculate the initial concentrations of the species. The concentration of HCl is 0.100 M, and it will completely ionize to form H+ and Cl-. The concentration of HCN is also 0.100 M, but it will only partially ionize. Therefore, the initial concentration of H+ ions will be 0.100 M from the HCl, and a small additional amount from the HCN.
Step 3: Since no NaOH has been added yet, we don't need to consider any reactions with NaOH. The pH of the solution will be determined solely by the H+ concentration.
Step 4: Use the formula for pH, which is pH = -log[H+]. In this case, [H+] is the concentration of H+ ions in the solution.
Step 5: Substitute the value of [H+] into the pH formula to calculate the pH of the solution. Remember that the concentration of H+ ions is the sum of the ions from the HCl and the HCN.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Chemistry
Acid-base chemistry involves the study of substances that can donate protons (acids) or accept protons (bases). In this context, HCl is a strong acid that completely dissociates in solution, while HCN is a weak acid that partially dissociates. Understanding the behavior of these acids in solution is crucial for predicting the pH changes during titration.
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Arrhenius Acids and Bases
Titration
Titration is a quantitative analytical method used to determine the concentration of a solute in a solution. In this scenario, NaOH is added to the acid solution to neutralize it. The point at which the amount of titrant (NaOH) added is stoichiometrically equivalent to the amount of acid present is known as the equivalence point, which is essential for calculating pH at various stages of the titration.
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03:04Acid-Base Titration
pH Calculation
pH is a measure of the acidity or basicity of a solution, calculated as the negative logarithm of the hydrogen ion concentration. At the start of the titration (0.0 mL NaOH added), the pH is determined solely by the concentrations of HCl and HCN. Understanding how to calculate pH from the concentrations of acids and bases is vital for solving the problem presented.
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01:30pH Calculation Example
Related Practice
Textbook Question
Calculate the pH of solutions prepared by:
(d) Mixing equal volumes of 0.20 M HCl and 0.50 M HNO3.
(Assume that volumes are additive.)
Textbook Question
The acidity of lemon juice is derived primarily from citric acid (H3Cit), a triprotic acid. What are the concentrations of H3Cit, H2Cit-, HCit2-, and Cit3- in a sample of lemon juice that has a pH of 2.37 and a total concentration of the four citrate-containing species of 0.350 M?
Textbook Question
A 40.0 mL sample of a mixture of HCl and H3PO4 was titrated with 0.100 M NaOH. The first equivalence point was reached after 88.0 mL of base, and the second equivalence point was reached after 126.4 mL of base.
(e) Sketch the pH titration curve, and label the buffer regions and equivalence points.
Textbook Question
The following pictures represent aqueous solutions of three acids HA1A = X, Y, or Z2; water molecules have been omitted for clarity.
(c) Which acid, if any, is a strong acid?
Textbook Question
The following pictures represent aqueous solutions of three acids HA1A = X, Y, or Z2; water molecules have been omitted for clarity.
(e) What is the percent dissociation in the solution of HZ?