======Molar Volume of Hydrogen======


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**Alternative titles:** Magnesium and Acid Gas Collection
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====Summary====                   
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====Procedure====  
  - Cut a short length of clean magnesium ribbon.  
  - Fill a trough or large beaker with water and invert a gas collection tube (graduated cylinder) full of water into it.  
  - Add dilute hydrochloric acid (or sulfuric acid) to a small flask or test tube.  
  - Place a pre-weighed amount of magnesium ribbon into the flask, and quickly connect the flask to the gas collection tube with delivery tubing.  
  - Allow the reaction to proceed as hydrogen gas is generated and bubbles collect in the inverted tube.  
  - When the reaction is complete, record the volume of hydrogen collected.  
  - Compare the measured volume with the theoretical volume calculated using the reaction equation and Avogadro’s law.



====Links==== 
AP Chem 3.4-Molar Volume of a Gas Lab: Tips and Calculations - Crowdedbeaker: 
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Determination of the molar Volume of a Gas at STP - 
North Carolina School of Science and Mathematics: 
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====Variations====  
  * Compare results at different temperatures to show the effect of conditions on molar volume.



====Safety Precautions====
  * Wear safety glasses and gloves.  
  * Handle acids with care; use only dilute solutions.  
  * Ensure apparatus is set up securely to avoid spills and breakages.  
  * Do not ignite the collected hydrogen; keep away from open flames or sparks.  
  * Dispose of acidic waste properly by diluting and neutralizing before disposal.




====Questions to Consider====
  * What is the balanced equation for the reaction between magnesium and hydrochloric acid? (Mg + 2HCl → MgCl₂ + H₂)  
  * How does the measured gas volume compare with the expected molar volume of a gas at room temperature and pressure (~24 dm³/mol)?  
  * Why is it important to collect the gas over water? (It allows capture of the gas without significant loss to the air.)  
  * What sources of error might cause the measured volume to differ from the theoretical value? (Gas loss during setup, incomplete reaction, temperature/pressure variations, or solubility of hydrogen in water.)