Hi there. I see you are working with the Idea Gas Law! :)
The first thing we need to do to solve this problem is be sure we understand what it is that we must find: pressure.
We also have to remember the value of R (the ideal gas constant) is 8.314 J/mol·K.
Next, let's pull that Ideal Gas Law equation out of our "toolbox."
PV = nRT
Since we want to solve for pressure, we should move the variables around so that P (for pressure) is alone.
P = nRT/V
Next, we need to check our units. All of those given, except for the one associated with temperature, will work. So we need to convert degrees Celsius to Kelvins.
K = ° C + 273.15
45.00° + 273.15 = 318.15 K
Now we can plug values in to the equation:
P = nRT/V
P = (81.5 mol) (8.314 J/mol·K) (318.15 K) / 45.5 L
Our unit for pressure is pascals.
P = 4,743.137 Pa
We need to consider significant figures before we write a final answer.
P = 4,743 Pa = 4.74 KPa
