a steel cylinder of oxygen with a volume of 15 L was available for medical purposes. The cylinder pressure decrease from 40.6 to 38.5 atm during which time the temperature remain at 24.0 °C how many moles of oxygen had been removed

To determine the number of moles of oxygen that had been removed from the cylinder, we can use the Ideal Gas Law equation:

PV = nRT

Where:
P = pressure
V = volume
n = number of moles
R = ideal gas constant
T = temperature

First, let's convert the temperature from Celsius to Kelvin by adding 273.15:
T = 24.0 °C + 273.15 = 297.15 K

Next, rearrange the Ideal Gas Law equation to solve for the number of moles:
n = PV / RT

Now, plug in the values:
P₁ = 40.6 atm
P₂ = 38.5 atm
V = 15 L
R = 0.0821 L·atm/(mol·K)
T = 297.15 K

Substitute these values into the equation:
n = (P₁ - P₂) * V / (R * T)

Calculate:
n = (40.6 atm - 38.5 atm) * 15 L / (0.0821 L·atm/(mol·K) * 297.15 K)

n = 2.1 atm * 15 L / (0.0821 L·atm/(mol·K) * 297.15 K)

n = 31.5 L·atm / (2.44 L·atm/(mol·K))

n ≈ 12.91 moles

Therefore, approximately 12.91 moles of oxygen had been removed from the cylinder.