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1 markThe Kinetic Theory of Gases

CAPE Physics Unit 1 · 2005 · Paper 2 · Question 9(b)(i)

A volume of 0.14 m³ of helium (molar mass 4 g/mol) at a temperature of 400 K has a pressure of 1.6 x 10⁵ Pa.

What is the mass of the helium?

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Other parts of this question

  1. 9(a)(i)Explain why the molecules of a gas do not all move at the same speed.[1 mark]
  2. 9(a)(ii)What is the meaning of the term r.m.s. speed? How is it calculated?[1 mark]
  3. 9(a)(iii)Derive the expression relating the r.m.s. speed of the molecules of an ideal gas to the pressure exerted by the gas: PV = (1/3)Nm c²[8 marks]
  4. 9(b)(ii)Find the r.m.s. speed of the helium molecules.[1 mark]
  5. 9(b)(iii)What would be the r.m.s. speed of oxygen molecules (molar mass 32 g/mol) at the same temperature of 400 K?[12 marks]

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