Question

The volume of a gas at 20°C is 200ml, if the temperature is reduced to -20°C at constant pressure. Its volume will be

Answer 1

Given :

➾ Initial volume = 200ml

➾ Initial temperature = 20°C

➾ Final temperature = -20°C

➾ Pressure remains constant.

To Find :

➛ Final volume of gas.

Concept :

➠ This question is completely based on the concept of Charle's law.

➠ As per this law : Pressure remaining constant, the volume of a fixed mass of a gas is directly proportional to its absolute temperature.

Mathematically,

✭ V/T = V'/T'

where

◕ V denotes initial volume

◕ T denotes initial temperature

◕ V' denotes final volume

◕ T' denotes final temperature

Conversion :

⇒ 0°C = 273K

⇒ 20°C = 273 + 20 = 293K

⇒ -20°C = 273 - 20 = 253K

Calculation :

➳ V/T = V'/T'

➳ 200/293 = V'/253

➳ V' = (253×200)/293

➳ V' = 172.7ml

Learn More :

✪ Boyle's law : At constant temlerature, the pressure of a fixed amount of gas varies inversely with its volume. (PV = P'V')

✪ Gay Lussac's law : At constant volume, Pressure of a fixed amount of gas varies directly with the temperature. (P/T = P'/T')

✪ Avogrado's law : Under similar conditions of temperature and pressure equal volume of all gases contain equal nimber of molecules.

Answer 2

Given :-

• Initial volume = 200 ml
• Initial temperature = 20℃
• Final temperature = -20℃
• Pressure remains constant.

Here we have to find :-

• The volume of gas

Note :- As per the question is based on the concept of Charle's Law.

★ It states that pressure remaining constant the volume of a fixed mass of a gas is directly proportional to its absolute temperature.

Mathematically :-

★ V/T = V'/T'

Solution :-

→ V/T = V'/T'

→ 200/293 = V'/253

→ V' = (253 × 200)/293

→ V' = 172.7 ml.