Podcast
Questions and Answers
Which of the following statements cannot be supported by the Arrhenius theory of acids and bases?
Which of the following statements cannot be supported by the Arrhenius theory of acids and bases?
state the function of a catalytic converter
state the function of a catalytic converter
To (catalyse reactions which) reduce the amount of harmful gases (e.g. carbon monoxide, unburnt petrol and nitrogen oxides) emitted by a vehicle.
Explain why the use of nanoparticles has greatly reduced the amount of precious metals
used to construct a catalytic converter.
Explain why the use of nanoparticles has greatly reduced the amount of precious metals used to construct a catalytic converter.
Nanoparticles have a very large surface area (to mass ratio).
This increases the frequency of collisions between the catalyst and the gases.
Therefore less material is required (compared to the bulk) to provide an equivalent surface area / to function effectively.
Explain, in terms of intermolecular forces, why the vapour pressure of hexane is much
higher than the other two liquids.
Explain, in terms of intermolecular forces, why the vapour pressure of hexane is much higher than the other two liquids.
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out of water, ethanol and hexane, which has highest boiling point? Justify answer (the table says water does but justify why)
out of water, ethanol and hexane, which has highest boiling point? Justify answer (the table says water does but justify why)
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Explain, in terms of the kinetic theory, why the vapour pressure of water increases with
increasing temperature.
Explain, in terms of the kinetic theory, why the vapour pressure of water increases with increasing temperature.
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Sample preparation: filtration Non-Polar Stationary phase: polymer- based matrix
Polar Mobile phase: 0.0035 mol L-1 H2SO4(aq)
Flow rate: 0.6 mL min-1
Oxalic acid- lowest retention time
Acetic acid- highest retention time
Which acidulant is likely to be the most polar? Justify your answer, making reference to the
role of intermolecular forces.
Sample preparation: filtration Non-Polar Stationary phase: polymer- based matrix Polar Mobile phase: 0.0035 mol L-1 H2SO4(aq) Flow rate: 0.6 mL min-1
Oxalic acid- lowest retention time Acetic acid- highest retention time
Which acidulant is likely to be the most polar? Justify your answer, making reference to the role of intermolecular forces.
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Study Notes
Arrhenius Theory of Acids and Bases
- Arrhenius theory defines acids as substances that increase H⁺ concentration in water and bases as substances that increase OH⁻ concentration.
- Limitations include compounds that behave like acids or bases without producing H⁺ or OH⁻ in solution, such as ammonia.
Function of a Catalytic Converter
- Catalytic converters convert harmful gases from vehicle exhaust into less harmful substances.
- Key reactions include the oxidation of carbon monoxide to carbon dioxide and reduction of nitrogen oxides.
Use of Nanoparticles in Catalytic Converters
- Nanoparticles provide a larger surface area for reactions, reducing the quantity of precious metals needed.
- Enhanced catalytic efficiency allows for lower metal loading without compromising performance.
Vapour Pressure of Hexane vs. Other Liquids
- Hexane has weak London dispersion forces, leading to higher vapour pressure due to easier molecule escape into the gas phase.
- Greater intermolecular forces in other liquids result in lower vapour pressures.
Boiling Points of Water, Ethanol, and Hexane
- Water has the highest boiling point due to strong hydrogen bonding between molecules.
- Ethanol exhibits hydrogen bonds too, but weaker than water, while hexane experiences only dispersion forces.
Vapour Pressure of Water and Temperature
- According to the kinetic theory, as temperature increases, water molecules gain kinetic energy, leading to more escape into the vapor phase.
- This results in higher vapour pressure at elevated temperatures.
Sample Preparation & Chromatography
- Filtration is used for sample preparation to separate solids from liquids.
- Non-polar stationary phase: polymer-based matrix facilitates interactions with non-polar compounds.
- Polar mobile phase (0.0035 mol L⁻¹ H₂SO₄(aq)) interacts preferentially with polar compounds.
Retention Times of Acids
- Oxalic acid shows the lowest retention time, indicating stronger interaction with the polar mobile phase.
- Acetic acid has the highest retention time due to weaker interactions compared to oxalic acid.
Polarity of Acidulants
- Oxalic acid is likely the most polar acidulant due to its ability to form hydrogen bonds and engage in dipole-dipole interactions.
- The presence of multiple functional groups increases its polarity compared to acetic acid.
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Description
Test your understanding of the Arrhenius theory of acids and bases with this quiz. Identify which statements align with the theory and which do not. Challenge your knowledge of fundamental concepts in chemistry!
