18.5.2 State and explain how the pH range of an acid-base indicator relates to its pKa value.
18.5.3 Identify an appropriate indicator for a titration, given the equivalence point of the titration and the pH range of the indicator
Showing posts with label Topic 18. Show all posts
Showing posts with label Topic 18. Show all posts
Monday, 17 November 2014
Topic 18.5: Indicators
18.5.1 Describe qualitatively the action of an acid-base indicator
18.5.2 State and explain how the pH range of an acid-base indicator relates to its pKa value.
18.5.3 Identify an appropriate indicator for a titration, given the equivalence point of the titration and the pH range of the indicator
18.5.2 State and explain how the pH range of an acid-base indicator relates to its pKa value.
18.5.3 Identify an appropriate indicator for a titration, given the equivalence point of the titration and the pH range of the indicator
Topic 18.4: Acid-base titrations
18.4.1 Sketch the general shapes of graphs of pH against volume for titrations involving strong and weak acids and bases, and explain their important features.
Topic 18.3: Salt hydrolysis
18.3.1 Deduce whether salts form acidic, alkaline or neutral aqueous solutions
Topic 18.2: Buffer solutions
18.2.1 Describe the composition of a buffer solution and explain its action
A buffer refers to something that acts to reduce the impact of one thing on another - little bit like a shock absorber. For example, buffer in the computer world are areas shared by hardware devices that operate at different speeds. In acid-base chemistry, a buffer acts to reduce the impact on pH of adding acid or base to a chemical system.
18.2.2 Solve problems involving the composition and pH of a specified buffer system
Factors that can influence buffers are Dilution and Temperature.
Dilution, Ka and Kb as equilibrium constants are not changed by dilution. Nor is the ratio of acid to salt concentration, as both components will be decreased by the same amount. Therefore, diluting a buffer does not change its pH.
Nonetheless, diluting a buffer does alter the amount of acid or base it can absorb without significant changes in pH - the so-called buffering capacity. This depends on the molar concentration of its components, so decrease as they are lowered by dilution.
Temperature affects the values of Ka and Kb. it accordingly affects the pH of the buffer. This is why a constant temperature should be maintained in all work involving buffers such as calibration of pH meters. Temperature fluctuations must also be minimized in many medical procedures such as blood transfusions, due to the effect on the buffers in the blood.
A buffer refers to something that acts to reduce the impact of one thing on another - little bit like a shock absorber. For example, buffer in the computer world are areas shared by hardware devices that operate at different speeds. In acid-base chemistry, a buffer acts to reduce the impact on pH of adding acid or base to a chemical system.
18.2.2 Solve problems involving the composition and pH of a specified buffer system
Factors that can influence buffers are Dilution and Temperature.
Dilution, Ka and Kb as equilibrium constants are not changed by dilution. Nor is the ratio of acid to salt concentration, as both components will be decreased by the same amount. Therefore, diluting a buffer does not change its pH.
Nonetheless, diluting a buffer does alter the amount of acid or base it can absorb without significant changes in pH - the so-called buffering capacity. This depends on the molar concentration of its components, so decrease as they are lowered by dilution.
Temperature affects the values of Ka and Kb. it accordingly affects the pH of the buffer. This is why a constant temperature should be maintained in all work involving buffers such as calibration of pH meters. Temperature fluctuations must also be minimized in many medical procedures such as blood transfusions, due to the effect on the buffers in the blood.
Topic 18.1: Calculations involving acids and bases
18.1.1 State the expression for the ionic product constant of water (Kw).
18.1.2 Deduce [H+(aq)] and [OH-(aq)] for water at different temperatures given Kw values
Since we know that
As the temperature increases, the equilibrium has shifted to the right. When it is shifted to the right this means the concentration of Hydrogen ions has increased thus lowering the pH. Thus the solution has a lower pH at higher temperature.
18.1.3 Solve problems involving [H+(aq)], [OH-(aq)], pH and pOH
18.1.4 State the equation for the reaction of any weak acid or weak base with water, and hence deduce the expressions of Ka and Kb
18.1.5 Solve problems involving solutions of weak acids and bases using the expression:
Ka x Kb = Kw
pKa + pKb = pKw
pH + pOH = pKw
18.1.6 Identify the relative strengths of acids and bases using values of Ka, Kb, pKa and pKb
18.1.2 Deduce [H+(aq)] and [OH-(aq)] for water at different temperatures given Kw values
Since we know that
As the temperature increases, the equilibrium has shifted to the right. When it is shifted to the right this means the concentration of Hydrogen ions has increased thus lowering the pH. Thus the solution has a lower pH at higher temperature.
18.1.3 Solve problems involving [H+(aq)], [OH-(aq)], pH and pOH
18.1.4 State the equation for the reaction of any weak acid or weak base with water, and hence deduce the expressions of Ka and Kb
18.1.5 Solve problems involving solutions of weak acids and bases using the expression:
Ka x Kb = Kw
pKa + pKb = pKw
pH + pOH = pKw
18.1.6 Identify the relative strengths of acids and bases using values of Ka, Kb, pKa and pKb
Topic 18: Acids and bases
Topic 18 of the IB HL Chemistry syllabus is the Acids and bases. IBO recommends to spend 10 hours on this topic.
This topic has 5 sub-chapters: "Calculations involving acids and bases", "Buffer solutions", "Salt hydrolysis", "Acid-base titrations" and "Indicators". Each are separated with numerical values in order of mentioned.
These are advanced HL syllabus statements, it is recommended to bring a Casio Graphical Calculator instead of Texas. Casio Calculators have the periodic table installed already.
This topic has 5 sub-chapters: "Calculations involving acids and bases", "Buffer solutions", "Salt hydrolysis", "Acid-base titrations" and "Indicators". Each are separated with numerical values in order of mentioned.
These are advanced HL syllabus statements, it is recommended to bring a Casio Graphical Calculator instead of Texas. Casio Calculators have the periodic table installed already.
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