Gas laws: Class 11 practice
Boyle's law: P₁V₁ = P₂V₂ at constant T. Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Kelvin scale
- Proportion
The idea behind gas laws
Boyle's law: P₁V₁ = P₂V₂ at constant T. Charles's law: V₁/T₁ = V₂/T₂ at constant P (T in K). Combined: P₁V₁/T₁ = P₂V₂/T₂.
Step-by-step method
- Write the known values with units; convert °C to K.
- Choose the law that keeps the right quantity constant.
- Solve for the unknown.
Worked example 1 (Basic)
2 L of gas at 4 atm is compressed at constant temperature to 7 atm. Find the new volume.
- V₂ = P₁V₁/P₂ = 8/7
- = 1.14 L
- Answer: 1.14 L
Worked example 2 (Standard)
11 L of gas at 93 °C is heated to 197 °C at constant pressure. Find the new volume.
- T₁ = 366 K, T₂ = 470 K
- V₂ = 11 × 470/366 = 14.13 L
- Answer: 14.13 L
Worked example 3 (Challenge)
A gas at 5 atm, 12 L, 267 K changes to 1 atm and 293 K. Find the new volume.
- V₂ = P₁V₁T₂/(T₁P₂)
- = 65.84 L
- Answer: 65.84 L
Common mistakes and misconceptions
- Using °C in Charles's law
- Using Boyle's law when temperature changes
Practice questions
- (Basic) 18 L of gas at 5 atm is compressed at constant temperature to 3 atm. Find the new volume.
- (Basic) 10 L of gas at 1 atm is compressed at constant temperature to 6 atm. Find the new volume.
- (Standard) 9 L of gas at 5 °C is heated to 195 °C at constant pressure. Find the new volume.
- (Standard) 14 L of gas at -2 °C is heated to 109 °C at constant pressure. Find the new volume.
- (Challenge) A gas at 5 atm, 14 L, 330 K changes to 2 atm and 451 K. Find the new volume.
- (Challenge) A gas at 5 atm, 15 L, 270 K changes to 5 atm and 439 K. Find the new volume.
Answer key with full working
- Q1: V₂ = P₁V₁/P₂ = 90/3 → = 30 L → Answer: 30 L
- Q2: V₂ = P₁V₁/P₂ = 10/6 → = 1.67 L → Answer: 1.67 L
- Q3: T₁ = 278 K, T₂ = 468 K → V₂ = 9 × 468/278 = 15.15 L → Answer: 15.15 L
- Q4: T₁ = 271 K, T₂ = 382 K → V₂ = 14 × 382/271 = 19.73 L → Answer: 19.73 L
- Q5: V₂ = P₁V₁T₂/(T₁P₂) → = 47.83 L → Answer: 47.83 L
- Q6: V₂ = P₁V₁T₂/(T₁P₂) → = 24.39 L → Answer: 24.39 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 gas laws 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.