Strategies:
1. Read the question carefully to extract all the given information:
- initial and final T, P, V
- no. of moles of gas, n
- unchanged conditions (constant T, P, V, n?)
For difficult or wordy questions, drawing a simple diagram will aid understanding.
2. Apply relevant gas law equations.
Constant T, Pi x Vi = Pf x Vf (Boyles’ law)
Constant P, Vi/ Ti = Vf/ Tf (Charles’ law)
Constant V, Pi/ Ti = Pf/ Tf
Constant T,P Vi/ ni = Vf/ nf (Avogadro's law)
Constant n,
3. When using the ideal gas equation,
PV = nRT
P : pressure of gas in Nm-2 or Pa.
V : volume of gas in m3
T : absolute temperature in Kelvins
n : number of moles of gas
R : Universal gas constant (8.314 J K-1 mol-1)
* remember to convert all conditions to S.I. units.
Many questions will present P, V, T in non S.I. units (e.g. atm, dm3, oC) to trick unsuspecting students.
