Chemistry practical: 1 Flashcards
Main goal of this practical
Measure the molar volume of gas
Preparing the acid
Place 30cm3 of ethanoic acid in a boiling tube
Apparatus to measure volume of gas collected
Set up apparatus, with a bung attached to boiling tube into the upturned cylinder with water
Weighing method for solid
Place around 0.05g of calcium carbonate in weighing bottle and weigh the test tube + contents
reweigh empty weighing bottle after
subtract to find exact mass of solid added
How is solid added to test tube?
Quickly remove bung and place into tube with ethanoic acid then put back
Why does the bung need to be replaced quickly?
To prevent gas loss so volume of gas can be accurately recorded
What measurement do we take?
Once reaction is over, measure volume of gas collected in measuring cylinder
Why is re weighing by mass done?
To ensure any calcium carbonate not added to boiling tube is accounted for
what is changed each time?
Repeat experiment by adding 0.05g more but do not exceed 0.4g
Why is there a limit on the mass of calcium carbonate added?
Because this will produce a lot of gas which will exceed the volume capacity in the measuring cylinder
Main problem of this experiment
Gas will escape when bung is being replaced
How can the main problem be overcome?
Include the calcium carbonate inside the vessel which can be added to acid by tipping rather than having to remove bung
Why don’t we use a strong acid?
Because this will mean a faster reaction, thus more gas released quicker. So more gas released when the bung is removed
If a gas syringe is used, what problem may happen and how do w fix it?
The plunger isn’t free moving so a lubricant is required because syringe sticks
CO2 and water problem
CO2 is slightly soluble in water therefore not all gas will be accurately measured
What affects volume of gas measured otehr than mass of solid used?
Temperature and pressure of room - ideal gas equation
pV = nRT
Finding molar volume
Plot volume of gas (y axis) to mass of solid used
Calculate moles of solid = moles of gas produced and read off graph volume of gAS given off in this number of moles
Molar volume = volume/moles of gas
