Domanda del libro di testo
Which of the following solutions has the greater buffer capacity: 100 mL of 0.30 M HNO2-0.30 M NaNO2 or 100 mL of 0.10 M HNO2-0.10 M NaNO2? Explain.
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Ch.17 - Applications of Aqueous Equilibria
McMurry8th EditionChemistryISBN: 9781292336145
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TOC.tableOfContents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Capitolo 17, Problema 67
Calculate the pH of a buffer solution that is 0.20 M in HCN and 0.12 M in NaCN. Will the pH change if the solution is diluted by a factor of 2? Explain.
Guida verificata passo dopo passo1
First, identify the acid and its conjugate base in the buffer solution. In this case, HCN is the weak acid and CN- (from NaCN) is the conjugate base.
Next, use the Henderson-Hasselbalch equation to calculate the pH of the buffer solution. The equation is pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base (CN-) and [HA] is the concentration of the acid (HCN). The pKa of HCN can be found in a table of acid dissociation constants.
Substitute the given concentrations into the Henderson-Hasselbalch equation and solve for pH.
To determine if the pH will change when the solution is diluted by a factor of 2, consider that the ratio of [A-]/[HA] will remain the same because both the acid and its conjugate base are being diluted by the same factor. Therefore, the pH of the solution will not change.
Finally, remember that the effectiveness of a buffer is determined by its capacity, which is the amount of acid or base the buffer can neutralize before the pH begins to change significantly. Diluting the buffer will decrease its buffer capacity, meaning it will be less able to resist changes in pH when an acid or base is added.
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Buffer Solutions
Buffer solutions are mixtures that resist changes in pH when small amounts of acid or base are added. They typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid. In this case, HCN (a weak acid) and NaCN (its conjugate base) form a buffer that helps maintain a stable pH.
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Percorso guidato
03:02
Buffer Solutions
Henderson-Hasselbalch Equation
The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It is expressed as pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the weak acid. This equation highlights the relationship between the concentrations of the acid and its conjugate base in determining the pH.
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Percorso guidato
02:40Henderson-Hasselbalch Equation
Dilution and pH Stability
When a buffer solution is diluted, the concentrations of both the weak acid and its conjugate base decrease proportionally. However, the ratio of [A-] to [HA] remains constant, which means the pH of the buffer does not change significantly upon dilution. This property is what makes buffers effective in maintaining pH levels in various chemical and biological processes.
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Percorso guidato
00:58Dilution Equation
Pratica correlata
Domanda del libro di testo
Calculate the pH of 0.375 L of a 0.18 M acetic acid–0.29 M sodium acetate buffer before and after the addition of (a) 0.0060 mol of KOH. Assume that the volume remains constant.
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Domanda del libro di testo
Which of the following gives a buffer solution when equal volumes of the two solutions are mixed?
(a) 0.10 M NH3 and 0.10 M HCl
(b) 0.20 M NH3 and 0.10 M HCl
(c) 0.10 M NH4Cl and 0.10 M NH3
(d) 0.20 M NH4Cl and 0.10 M NaOH
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