Asked in Premeth Test 6 — Thermodynamics (physics)Moderate

Work doen by air when it expands from 50 liters to 150 liters at a constant pressure of 2 atmospheres is:

Correct answer: A. 2 x 10^4 Joules

  • A. 2 x 10^4 Joules
  • B. 2 x 10^5 x 100 Joules
  • C. 2x100 Joules
  • D. 2 x 10^-5 x 100 Joules

Explanation

To calculate the work done by a gas expanding at constant pressure, use the formula W = P∆V. The pressure is given as 2 atmospheres, which needs to be converted to Pascals: 2 atm = 2 x 1.01 x 10⁵ Pa. The change in volume ∆V is the difference between the final and initial volumes, which is 150 liters - 50 liters = 100 liters. Convert the volume from liters to cubic meters: 100 liters = 100 x 1/1000 m³ = 0.1 m³.Therefore, W = 2 x 1.01 x 10⁵ Pa x 0.1 m³ = 2.02 x 10⁴ Joules. However, based on significant figures and rounding, this is approximated to 2 x 10⁴ Joules, which is correctly represented by Option A.Options B, C, and D are incorrect due to errors in unit conversion or misunderstanding the formula.

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About Thermodynamics

Thermal equilibrium and heat explain how temperature and energy transfer are related, while molar specific heats describe the heat required by a gas at constant volume or constant pressure. The first law connects heat supplied, work done and change in internal energy, with sign conventions kept distinct from temperature changes.

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