======Molecular Mass of Butane======


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**Alternative titles:** Molar Mass of Butane by Gas Collection
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====Summary====                   
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====Procedure====  
  - Fill a large container with water and invert a graduated cylinder full of water into it. Clamp the cylinder securely.  
  - Weigh the cigarette lighter to obtain its initial mass.  
  - Insert the lighter’s nozzle under the mouth of the inverted graduated cylinder and release butane gas so that it displaces the water, collecting a measurable volume of gas.  
  - After collecting sufficient gas, remove the lighter and reweigh it to find the mass of butane released.  
  - Record the volume of butane gas collected, the temperature of the water bath, and the atmospheric pressure.  
  - Correct the collected gas volume for water vapor pressure.  
  - Use the ideal gas law (PV = nRT) to calculate the moles of butane.  
  - Determine the molar mass by dividing the mass of butane released by the calculated number of moles.



====Links==== 
Experiment 18 - The Molar Mass of Butane - Phil Reedy: 
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Determining the Molar Mass of Butane - Lab Hamster: 
{{youtube>OiQmzia0-Y8?}}\\

📄 Molar Mass of Butane - Flinn Scientific: [[https://www.flinnsci.com/api/library/Download/a2be5b406f58415b80fbcc3c02c9d932?srsltid=AfmBOop_1ugq9j-kmdhQpOIqqcOoaF4pfJRkr1_Q2bIzTOPJdCVcmX2u]]\\

====Variations====
  * Repeat the experiment with different collected volumes to improve accuracy. 
  * Collect gases from other small lighters or gas cartridges to compare calculated molar masses.



====Safety Precautions====
  * Butane is highly flammable—keep flames and sparks away from the experiment.  
  * Perform in a well-ventilated area to avoid buildup of butane vapors.  
  * Wear safety goggles to protect from splashes or accidents.  
  * Handle the lighter carefully; do not overheat or damage it.  
  * Dispose of excess butane outdoors, not in a closed room.




====Questions to Consider====
  * Why must the gas volume be corrected for water vapor pressure? (Because the collected gas is a mixture of butane and water vapor.)  
  * How does temperature affect the calculated number of moles of gas? (Higher temperatures increase gas volume at constant pressure, leading to different mole calculations.)  
  * What assumptions are made when using the ideal gas law? (That the gas behaves ideally, with negligible molecular volume and no intermolecular forces.)  
  * How would experimental errors such as gas leaks or inaccurate weighing affect the calculated molar mass? (They would lead to incorrect mass or volume measurements, skewing the molar mass result.)