Ideal gas equation: Class 11 practice
PV = nRT with R = 0.0821 L atm/(mol K) or 8.314 J/(mol K). Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Mole concept
The idea behind ideal gas equation
PV = nRT with R = 0.0821 L atm/(mol K) or 8.314 J/(mol K). It links pressure, volume, moles and temperature; density d = PM/RT.
Step-by-step method
- Pick R to match the units.
- Convert T to K.
- Rearrange PV = nRT for the unknown.
Worked example 1 (Basic)
Find the pressure of 4.5 mol of gas in 24 L at 397 K.
- P = nRT/V = 4.5 × 0.0821 × 397/24
- = 6.111 atm
- Answer: 6.111 atm
Worked example 2 (Standard)
How many moles of gas occupy 6 L at 4 atm and 356 K?
- n = PV/RT
- = 0.821 mol
- Answer: 0.821 mol
Worked example 3 (Challenge)
Find the density of a gas of molar mass 44 g/mol at 3 atm and 342 K.
- d = PM/RT
- = 4.701 g/L
- Answer: 4.701 g/L
Common mistakes and misconceptions
- Mixing R units
- Using °C
Practice questions
- (Basic) Find the pressure of 5 mol of gas in 49 L at 364 K.
- (Basic) Find the pressure of 4 mol of gas in 8 L at 292 K.
- (Standard) How many moles of gas occupy 32 L at 1 atm and 373 K?
- (Standard) How many moles of gas occupy 6 L at 1 atm and 492 K?
- (Challenge) Find the density of a gas of molar mass 32 g/mol at 2 atm and 280 K.
- (Challenge) Find the density of a gas of molar mass 16 g/mol at 3 atm and 337 K.
Answer key with full working
- Q1: P = nRT/V = 5 × 0.0821 × 364/49 → = 3.049 atm → Answer: 3.049 atm
- Q2: P = nRT/V = 4 × 0.0821 × 292/8 → = 11.987 atm → Answer: 11.987 atm
- Q3: n = PV/RT → = 1.045 mol → Answer: 1.045 mol
- Q4: n = PV/RT → = 0.149 mol → Answer: 0.149 mol
- Q5: d = PM/RT → = 2.784 g/L → Answer: 2.784 g/L
- Q6: d = PM/RT → = 1.735 g/L → Answer: 1.735 g/L
Syllabus note
This skill is listed under "States of Matter" for Class 11 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.
Related practice and notes
Frequently asked questions
Which chapter is ideal gas equation in?
"States of Matter", Class 11 Chemistry (NCERT/CBSE). Other boards may place it differently.
How were the answers checked?
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.