An evacuated glass bulb is first filled with a measured mass of neon gas and then
CHEMISTRY · Multi-part · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
An evacuated glass bulb is first filled with a measured mass of neon gas and then, without otherwise disturbing the system, an additional measured mass of argon gas is introduced. Both gases are chemically inert toward each other under the conditions of the experiment.
(a) Explain, using particulate–level reasoning, why the total amount of substance (in moles) present in the bulb after both additions equals the numerical sum of the separate amounts of neon and argon introduced.
(b) Identify two specific physical or chemical circumstances under which the additivity of the amounts of substance would no longer hold for a two–component gas mixture.
(c) The experimenter adds 0.500g of Ne and subsequently 1.000g of Ar. Given that the molar masses are 20.18gmol−1 for Ne and 39.95gmol−1 for Ar, describe—without carrying out an explicit numerical calculation—the algebraic expression that would be used to determine the total number of atoms now contained in the bulb in terms of Avogadro’s constant NA.