A container has a volume of #9 L# and holds #18 mol# of gas. If the container is expanded such that its new volume is #54 L#, how many moles of gas must be injected into the container to maintain a constant temperature and pressure?

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Answer 1 · 2016-11-18T17:31:16

The answer is #=90mol#

Let's work with the ideal gas equation #PV=nRT#

With the initial conditions,

#P_1V_1=n_1RT_1#

With the final conditions,

#P_1V_2=n_2RT_1#

as the temperature and the pressure do not change,

From those 2 equations,

#P_1=(n_1RT_1)/V_1=(n_2RT_1)/V_2#

#n_2=(V_2n_1)/V_1#

#V_1=9l#

#V_2=54l#

#n_1=18mol#

#n_2=54*18/9=108 mol#

Number of moles of gas to be injected #=n_2-n_1#

#=108-18=90mol#