Molar volume of gas

• Measure of the molar volume of a gas

  1. Set up the apparatus to capture and measure gas evolved from a reaction in the boiling tube

  2. Place 30 cm3 of 1 mol dm−3 ethanoic acid in the boiling tube

  3. Place approximately 0.05 g of calcium carbonate in a test tube. Weigh the test tube and its contents accurately

  4. Remove the bung from the boiling tube and tip the calcium carbonate into the boiling tube. Quickly replace the bung in the boiling tube

  5. Once the reaction is over, measure the volume of gas produced

  6. Reweigh the test tube that contained the calcium carbonate

  7. Repeat the experiment six more times, increasing the mass of calcium carbonate by about 0.05 g each time. Do not exceed 0.40 g of calcium carbonate
• Analysis of results


  1. Plot a graph of mass of calcium carbonate (on the x-axis) against volume of carbon dioxide collected (on the y-axis). Draw a straight line of best fit – this line must pass through the origin

  2. Use your graph to find the volume of carbon dioxide that would be made from 0.25 g of calcium carbonate

  3. In this reaction, one mole of calcium carbonate makes one mole of carbon dioxide. Calculate the number of moles of calcium carbonate in 0.25 g and hence calculate the volume of one mole of carbon dioxide gas in dm3
• What is the objective?

  to find the volume of one mole of carbon dioxide gas
• What are the safety precautions?

  wear eye protection

  remove the bung if the delivery tube gets blocked

  avoid skin contact with the ethanoic acid
• Diagram

  A) 30 cm3 ethanoic acid

  B) stand and clamp

  C) 100cm3 measuring cylinder

  D) water

  
• Write a chemical equation for the reaction between ethanoic acid and calcium carbonate

  CaCO3 + 2CH3COOH -> Ca(CH3COO2) + CO2 + H2O
• Why is it more accurate to find the mass of the calcium carbonate used by weighing the test tube containing the calcium carbonate and then reweighing the test tube after the calcium carbonate has been tipped out, rather than by weighing the empty test tube at the start?

  Allows for the mass of any calcium carbonate that remains in the test tube after tipping it out.
• Identify the major source of error caused by the procedure

  Gas loss before replacing the bung.
• What change to the procedure/apparatus could you make to eradicate this error?

  Use tube containing the acid inside the vessel containing the calcium carbonate - tip to mix the reagent.