Practical 1: molar volume of a gas

Question 1

How can you measure the volume of gas released from a reaction?

Answer 1

Using a gas syringe connected to a bung (via a tube) which stoppers the conical flask containing the reactants. As gas is released it pushes the syringe outwards.

Question 2

What is the weighing by difference method?

Answer 2

It is a method to weigh materials accurately.

Mass of substance = Mass of weighing dish and substance - Mass of dish after substance has been transferred.

Question 3

How would you carry out an experiment to measure the molar volume of a gas?

Answer 3

React ethanoic acid and solid calcium carbonate together. Using a gas syringe, measure the volume of gas released. Repeat for increasing masses of CaCO3.

Question 4

What are some issues with this experiment?

Answer 4

1. Some gas may escape before the bung is added.
2. Different carbonate solids may have slight differences in mass and S.A leading to different rates.
3. Some CO2 dissolves in water so you are not measuring exact volume.

Question 5

How do you prevent gas escaping?

Answer 5

1. Place the solid reactant in a small test tube inside a conical flask.
2. Secure the test tube upright using a stopper and thread.
3. To start the reaction, gently move the flask to tip the test tube, mixing the solid with the liquid.

Question 6

How would you analyse this data?

Answer 6

1. Plot mass of CaCO3 (x-axis) against volume of gas.
2. Draw a line of best fit that passes through the origin.
3. This reaction, CaCO3 to CO2 is a 1:1 ratio. You could use this to calculate the volume of 1 mol of carbon dioxide gas.