PAG 1 - Mole Determination of the composition of copper(II) carbonate

Question 1

Describe how to set up the apparatus to measure the volume of gas produced in a reaction

Answer 1

A gas syringe or an upsidedown water field measuring cylinder in trough (bowl) of water may be used to collect the gas

Question 2

How can the number of moles of CO2 be calculated from the volume of CO2 collected during an experiment?

Answer 2

• If at room temperature and pressure (RTP), use the equation n = V/24 where V is the volume in dm^3.
• If not at RTP, rearrange The ideal gas law PV equals NRT and plug the numbers of R (8.31), T in Kelvin, P in pascals and V in m^3

Question 3

What is used to accurately measure mass

Answer 3

A digital balance that records mass to 2 decimal places

Question 4

CuCO3 reacts with HCl to produce 15 moles of CO2. How many moles of CuCO3 reacted

Answer 4

CuCO3 + 2HCl —> CuCl2 + H20 + CO2

Ratio of CuCO3 to CO2 = 1:1

15 moles of CuCO3 reacted

Question 5

How could you find the percentage of mass of CuCO3 in CuCO3.Cu(OH)2

Answer 5

1. Record the mass of CuCO3.Cu(OH)2
2. React with acid and measure the volume of CO2 collected. Use this to work out the number of moles of CO2 produced (number of moles = volume in dm^3/24)
3. Use the ratio in the chemical equation to work out the number of moles of CuCO3 that reacted
4. Calculate the mass of CuCO3
5. Calculate the percentage of mass of CuCO3 in the original sample ( mass of CuCO3/ mass of CuCO3.Cu(OH2)

Question 6

Why is it important to rapidly put the bung into the conical flask after adding sulphuric acid to CuCO3.Cu(OH)2

Answer 6

The reaction starts as soon as the acid is added so CO2 Will start to be produced. To reduce the amount of CO2 that escapes, the bung should be inserted rapidly

Question 7

Give three possible sources of error when investigating the volume of gas produced in a reaction

Answer 7

• Some gas could have escaped before the bung is put in the conical flask
• The reaction may be incomplete
• Some gas may dissolve in the water meaning a smaller volume would have been collected

Question 8

What safety precautions should be taken when conducting an experiment with CuCO3.Cu(OH)2 and sulphuric acid

Answer 8

• CuCO3.Cu(OH)2 is harmful if swallowed, so avoid putting it near your face and wash your hands after use it is also an irritant so wear safety goggles and avoid contact with skin
• H2SO4 causes skin and eye irritation so wear safety goggles and avoid contact with skin