9702 · 15.2
Equation of state flashcards
Revision flashcards for Cambridge 9702 Equation of state (syllabus 15.2). Flip, recall, then mark a real past-paper question.
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What are the two fundamental assumptions for an ideal gas?
Its molecules have no intermolecular forces and occupy negligible volume.
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Which temperature scale must always be used for all gas law calculations?
Absolute temperature (Kelvin, K).
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State the relationship described by Boyle's Law.
For a fixed mass of gas at constant temperature, its pressure is inversely proportional to its volume (PV = constant).
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Write down the Ideal Gas Equation that uses the number of moles.
PV = nRT
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How is the Boltzmann constant (k) related to the molar gas constant (R) and Avogadro constant (N_A)?
k = R/N_A
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State Charles' Law.
For a fixed mass of gas at constant pressure, its volume is directly proportional to its absolute temperature (V/T = constant).
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What is the Pressure Law (Gay-Lussac's Law)?
For a fixed mass of gas at constant volume, its pressure is directly proportional to its absolute temperature (P/T = constant).
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What are the standard units for pressure (P), volume (V), and temperature (T) in the Ideal Gas Equation?
Pressure (P) in Pascals (Pa), Volume (V) in cubic metres (m³), Temperature (T) in Kelvin (K).
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How do you convert Celsius (°C) to Kelvin (K)?
Add 273.15 (or 273 for A-Level calculations) to the Celsius value. T(K) = T(°C) + 273.15.
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What is the value and unit of the molar gas constant (R)?
R = 8.31 J mol⁻¹ K⁻¹
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State the Combined Gas Law for a fixed mass of gas.
For a fixed amount of gas, the ratio of the product of pressure and volume to the absolute temperature is constant. (P₁V₁)/T₁ = (P₂V₂)/T₂.
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Under what conditions does a real gas most closely approximate an ideal gas?
At low pressure and high temperature.
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What does the Boltzmann constant (k) represent?
It is a proportionality factor that relates the average kinetic energy of particles in a gas with the thermodynamic temperature. It is effectively the gas constant per molecule.
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What is Avogadro's constant (N_A) and what is its value?
It is the number of constituent particles (e.g., atoms or molecules) per mole of a substance. Its value is 6.02 × 10²³ mol⁻¹.