A cold trap is set up to cause molecules to linger near the suction in a vacuum system. If the cold trap has an effective volume of 0.200 L and is maintained at 13.0 K, how many molecules are in it at 10.0 Pa of pressure? (Avogadro's number is 6.022 × 10²³ molecules/mol, and the universal gas constant is 8.314 J/mol•K. Assume the behavior of an ideal gas.) A) 1.11 × 10¹⁹ molecules B) 1.10 × 10²² molecules C) 7.71 × 10²⁰ molecules D) 7.71 × 10²³ molecules

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Quizplus · Accepted Answer

Using the ideal gas law PV = nRT, we can solve for n (number of moles) and then multiply by Avogadro's number to find the number of molecules. Substituting the given values: P = 10.0 Pa, V = 0.200 L = 0.0002 m³, R = 8.314 J/mol•K, T = 13.0 K, we find n = PV/RT = (10.0 * 0.0002) / (8.314 * 13.0) = 1.11 × 10^-5 moles. Multiplying by Avogadro's number gives approximately 1.11 × 10^19 molecules.

A Cold Trap Is Set Up to Cause Molecules to Linger