Core Practical 1

Question 1

Give 2 reasons why the exact volume of gas may not be measured when CaCO3 reacts with acid.

Answer 1

As CO2 is slightly soluble so the exact volume isn’t measured.
Gas escapes between addition of CaCO3 and sealing the bung (or bung may not be airtight)

Question 2

How can you ensure that you know the amount of CaCO3 ending up in reaction mixture?

Answer 2

When transferring the solid it’s important to weigh the tube before and after the addition of the CaCO3

Question 3

What is Avogadro’s law?

Answer 3

Equal volumes of gases at same temp and pressure will contain equal number of molecules

Question 4

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

Answer 4

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

Question 5

What is the weighing by the difference method?

Answer 5

an accurate method to weigh materials. Mass of substance = mass of weighing dish and substance - mass of dish after substance transferred

Question 6

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

Answer 6

React ethanoic acid and calcium carbonate together.

Using a gas syringe, measure the volume of gas released. Repeat for increasing masses of CaCO3

Question 7

How would you analyse this data?

Answer 7

Plot a graph of mass of CaCO3 (x-axis) against volume of CO2 collected (y-axis)
Draw line of best fit through origin
Calculate moles in 0.25g and use to to determine molar volume (1:1) CaCO3:CO2

Question 8

How would the use of a stronger acid affect the measurement of a molar volume of a gas?

Answer 8

Use of a stronger acid = faster reaction therefore greater loss of gas when calcium carbonate added to acid.