Question

A piston cylinder holds a 3.00 L volume of air at 300.0 K.The cylinder holds the gas at 3.25 atm pressure.How many moles of air are present in the cylinder under these conditions?A) 0.364B) 0.483C) 0.396D) 0.443

Answer 1

Step 1

Gas here is assumed to be ideal. Then, the next equation is applied:

$p\text{ x V = n x R x T \lparen1\rparen}$

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Step 2

Information provided:

p = pressure = 3.25 atm

V = volume = 3.00 L

n = number of moles = unknown

T = absolute temperature = 300.0 K

R = gas constant according to the units = 0.082 atm L/mol K

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Step 3

n is found from (1):

$\begin{gathered} \frac{p\text{ x V}}{R\text{ x T}}=n \\ \frac{3.25\text{ atm x 3.00 L}}{0.082\text{ }\frac{atm\text{ L}}{mol\text{ K}}x300.0\text{ K }}=\text{ 0.396 moles} \end{gathered}$

Answer: C) n = 0.396 moles