Chemistry: The Central Science (13th Edition)

Published by Prentice Hall
ISBN 10: 0321910419
ISBN 13: 978-0-32191-041-7

Chapter 10 - Gases - Exercises: 10.31


B has a molar mass of 60, A has a molar mass of 30

Work Step by Step

We are given two flasks with equal volumes and they are both at the same temperature. From the ideal gas law, we have: PV = nRT If V and T are constant, it means only the number of moles is different. We are told the pressure of A is Xatm and B is 0.5X atm. Since the pressure in B is half of the pressure in A, then B must have half the number of moles of substance. They both have 1.2g so that means the molar masses must be different. Since B has half the number of moles, the molar mass must be twice as large so: B has a molar mass of 60, A has a molar mass of 30
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