9701 · 4.1
The gaseous state: ideal and real gases and pV = nRT flashcards
Revision flashcards for Cambridge 9701 The gaseous state: ideal and real gases and pV = nRT (syllabus 4.1). Flip, recall, then mark a real past-paper question.
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What are the two main assumptions made for an ideal gas?
1. The gas particles themselves have negligible volume (they are point masses). 2. There are no intermolecular forces of attraction or repulsion between the particles.
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What is an elastic collision?
A collision in which the total kinetic energy of the colliding particles is conserved. Ideal gas particles are assumed to undergo perfectly elastic collisions.
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What is the ideal gas equation?
pV = nRT
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What are the standard SI units for each variable in the ideal gas equation?
p: Pascals (Pa) V: cubic metres (m³) n: moles (mol) T: Kelvin (K)
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What is the value and what are the units of the molar gas constant, R?
R = 8.31 J mol⁻¹ K⁻¹ (Joules per mole per Kelvin).
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How do you convert from degrees Celsius (°C) to Kelvin (K)?
K = °C + 273.15 (For A-Level, using +273 is usually sufficient).
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How do you convert a volume in cm³ to m³?
Divide by 1,000,000 (or multiply by 10⁻⁶). 1 m³ = 1,000,000 cm³.
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How do you convert a volume in dm³ to m³?
Divide by 1,000 (or multiply by 10⁻³). 1 m³ = 1,000 dm³.
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Under what two conditions do real gases deviate most from ideal behaviour?
High pressure and low temperature.
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Why do real gases deviate from ideal behaviour at high pressure?
At high pressure, particles are forced close together. The volume of the particles themselves becomes significant compared to the total volume, violating an ideal gas assumption.
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Why do real gases deviate from ideal behaviour at low temperature?
At low temperature, particles have less kinetic energy. Intermolecular forces become significant and can cause particles to 'stick' together, reducing the pressure exerted on the container walls compared to an ideal gas.