Anyone know how to calculate moles? for chem.

if the atmospheric pressure in the laboratory is 1.2 atm, how many moles of gas were in each syringe?
^ this is my question

trial 1:
volume for syringe: 4.2 ml
temperature: 0.9 - c

trial 2:
volume for syringe: 4.1 ml
temperature: 0.9 - c

if you could also explain well i would appreciate it!

Trial 1 : n = 0.0002241 moles

Trail 2 :  n = 0.0002188 moles

Explanation:

Let's bring out the data in the question;

Pressure (P) = 1.2 atm

Number of moles (n) = ?

Both trials contain different values of Volume (V) and temperature (T)

The equation that relates all four parameters (V, T, P and n) is the ideal gas equation. It is given as;

PV = nRT where R = gas constant = 0.0821 L atm K−1 mol−1

Soving for n, we have;

n = PV / RT

Trial 1

Volume (V) = 4.2 ml = 0.0042 L (Converting to L by dividing by 1000)

Temperature (T) = 0.9 + 273 = 273.9K (Converting to Kelvin temperature)

n = (1.2 * 0.0042) / (0.0821 * 273.9)

n = 0.00504 / 22.48719

n = 0.0002241 moles

Trial 2

Volume (V) = 4.1 ml = 0.0041 L (Converting to L by dividing by 1000)

Temperature (T) = 0.9 + 273 = 273.9K (Converting to Kelvin temperature)

n = (1.2 * 0.0041) / (0.0821 * 273.9)

n = 0.00492 / 22.48719

n = 0.0002188 moles