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Reviewed CSCA Chemistry question · Easy

A balloon contains 0.50 mol of an ideal gas at a pressure of 1.2 atm and a temperature of 27°C. The gas is compressed isothermally until its volume is halved. What is the new pressure in atm?

  1. 0.60
  2. 2.4
  3. 1.2
  4. 0.30
Show the answer and explanation

Correct answer

B. 2.4

Principle or equation

For an isothermal process, Boyle's law applies: P1V1 = P2V2. If volume is halved, pressure doubles.

Why this answer is correct

Initial pressure P1 = 1.2 atm. Volume is halved, so V2 = V1/2. Using P1V1 = P2V2, we get P2 = P1(V1/V2) = 1.2 atm × 2 = 2.4 atm. Temperature and amount are constant, so the ideal gas law reduces to Boyle's law.

Example

If P1 = 1.2 atm and V2 = 0.5 V1, then P2 = 2.4 atm.

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