Step 1
The gas is assumed to be ideal. Therefore, it is applied the next formula:
p x V = n x R x T (1)
p = pressure = 1 atm
T = temperature = 2.5 °C; in K => T = 2.5 °C + 273 = 275.5 K
V = volume = 58.4 L
R = gas constant = 0.082 atm L/mol K (according to the units of the variables)
n = number of moles = unknown
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Step 2
n is cleared from (1):
p x V/R x T = (1 atm x 58.4 L)/(0.082 atm L/mol K x 275.5 K) = 2.6 moles approx.
Answer: n = 2.6 moles