{"questions":[{"id":"mdcat-chem-gas-01","v":1,"subject":"chemistry","chapter":"gases","seed":true,"difficulty":1,"stem":"Boyle's law states that, at constant temperature, the volume of a fixed mass of gas is:","options":["Directly proportional to pressure","Inversely proportional to pressure","Directly proportional to temperature","Independent of pressure"],"answer":1,"explain":{"en":"Boyle's law: PV = constant at constant temperature and amount of gas, so V ∝ 1/P. Doubling the pressure halves the volume.","ur":"بوائل کا قانون: درجہ حرارت اور گیس کی مقدار مستقل ہو تو PV مستقل رہتا ہے، یعنی V ∝ 1/P۔ دباؤ دگنا کریں تو حجم آدھا ہو جاتا ہے۔"},"source":{"kind":"parcha-original"},"status":"sample","exam":"mdcat"},{"id":"mdcat-chem-gas-02","v":1,"subject":"chemistry","chapter":"gases","difficulty":2,"stem":"A gas occupies 2 dm³ at 300 K. At constant pressure, its volume at 600 K will be:","options":["1 dm³","2 dm³","6 dm³","4 dm³"],"answer":3,"explain":{"en":"Charles's law: V/T is constant at constant pressure (T in kelvin). Doubling T from 300 K to 600 K doubles V from 2 dm³ to 4 dm³.","ur":"چارلس کا قانون: مستقل دباؤ پر V/T مستقل رہتا ہے (T کیلون میں)۔ T کو 300 K سے 600 K کرنے پر حجم 2 dm³ سے 4 dm³ ہو جاتا ہے۔"},"source":{"kind":"parcha-original"},"status":"sample","exam":"mdcat"},{"id":"mdcat-chem-gas-03","v":1,"subject":"chemistry","chapter":"gases","difficulty":1,"stem":"The value of the general gas constant R in SI units is:","options":["8.314 J K⁻¹ mol⁻¹","0.0821 J K⁻¹ mol⁻¹","1.987 J K⁻¹ mol⁻¹","22.4 J K⁻¹ mol⁻¹"],"answer":0,"explain":{"en":"R = 8.314 J K⁻¹ mol⁻¹. The same constant is 0.0821 dm³ atm K⁻¹ mol⁻¹ and about 1.987 cal K⁻¹ mol⁻¹; the units decide which number to use.","ur":"R = 8.314 J K⁻¹ mol⁻¹۔ یہی مستقل 0.0821 dm³ atm K⁻¹ mol⁻¹ اور تقریباً 1.987 cal K⁻¹ mol⁻¹ بھی ہے؛ اکائیاں طے کرتی ہیں کہ کون سا عدد لیا جائے۔"},"source":{"kind":"parcha-original"},"status":"sample","exam":"mdcat"},{"id":"mdcat-chem-gas-04","v":1,"subject":"chemistry","chapter":"gases","difficulty":1,"stem":"One mole of an ideal gas at 0 °C and 1 atm occupies about:","options":["11.2 dm³","24.0 dm³","22.4 dm³","44.8 dm³"],"answer":2,"explain":{"en":"At 273 K and 1 atm (the STP used in Pakistani textbooks), the molar volume of an ideal gas is 22.414 dm³. At room temperature (about 25 °C) it is about 24 dm³.","ur":"273 K اور 1 atm پر (پاکستانی نصاب کا STP) ایک مول مثالی گیس کا حجم 22.414 dm³ ہے۔ کمرے کے درجہ حرارت (تقریباً 25 °C) پر یہ تقریباً 24 dm³ ہوتا ہے۔"},"source":{"kind":"parcha-original"},"status":"sample","exam":"mdcat"},{"id":"mdcat-chem-gas-05","v":1,"subject":"chemistry","chapter":"gases","difficulty":2,"stem":"Under the same conditions, which gas diffuses fastest?","options":["O₂","CO₂","He","H₂"],"answer":3,"explain":{"en":"Graham's law: rate of diffusion ∝ 1/√M. Hydrogen has the smallest molar mass (2 g/mol), so it diffuses fastest; helium (4) is next.","ur":"گراہم کا قانون: پھیلاؤ کی رفتار ∝ 1/√M۔ ہائیڈروجن کا مولر ماس سب سے کم (2 g/mol) ہے، اس لیے یہ سب سے تیز پھیلتی ہے؛ اس کے بعد ہیلیم (4)۔"},"source":{"kind":"parcha-original"},"status":"sample","exam":"mdcat"},{"id":"mdcat-chem-gas-06","v":1,"subject":"chemistry","chapter":"gases","difficulty":2,"stem":"Real gases deviate most from ideal behaviour at:","options":["High pressure and low temperature","Low pressure and high temperature","Low pressure and low temperature","High temperature only"],"answer":0,"explain":{"en":"At high pressure, the volume of the molecules themselves is no longer negligible; at low temperature, attractive forces between molecules matter. Both break the ideal-gas assumptions.","ur":"زیادہ دباؤ پر مالیکیولز کا اپنا حجم نظرانداز نہیں ہو سکتا، اور کم درجہ حرارت پر مالیکیولز کی باہمی کشش اہم ہو جاتی ہے۔ دونوں مثالی گیس کے مفروضے توڑتے ہیں۔"},"source":{"kind":"parcha-original"},"status":"sample","exam":"mdcat"}]}