Measuring gas volumes

Question 1

Method for moles determination (determination of composition of copper 2 carbonate)

Answer 1

• Set up the apparatus using a 100cm^3 measuring cylinder and a 250cm^3 conical flask.
• Weigh 1.5g of CuCO3.Cu(OH)2, and add it to the conical flask.
• Measure 50cm^3 of H2SO4 in a 50cm^3 measuring cylinder.
• Add the H2SO4 into the conical flask and immediately insert the stopper, and the gas collects in the measuring cylinder.
• Record the final volume of carbon dioxide in the measuring cylinder.

Question 2

Potential errors and corrections

Answer 2

• Some CO2 may escape before the bung is inserted- inset bung as soon as acid has been poured into conical flask.
  -Some copper carbonate may not react- swirl the conical flask to mix the contents, to ensure the reaction goes to completion.
  -Some copper carbonate may remain in the apparatus and may not be fully transferred to the conical flask.

Question 3

Potential errors in using a gas syringe

Answer 3

• Gas escapes before bung inserted
• Syringe sticks
• Some gases may not be soluble in water, so the true amount of gas is not measured