If question asks why this experiment wasn’t carried out at this xyz high temperature
→ dangerous
→ reaction will be far too fast to notice a particular observation/ note down a specific reading.
Anytime acid is being added to a solution containing carbonate ions even if you have already
identified them in a previous row of the table you still have to mention that effervescence is
observed. - Very few candidates realised that all these reactions were on the same mixture
which they had been told contained carbonate and sulfate. As a result, the nitric acid would also
react with the carbonate and produce effervescence of carbon dioxide here as well as in the
barium chloride test.
pipettes and burettes are accurate pieces of measuring apparatus. Pipettes are designed to
deliver one volume accurately such as how a 25 cm3 pipette will accurately measure
25cm3 nothing less, whereas burettes can deliver anything in between 0.0 cm3 and
(usually) 50.0 cm3. Measuring cylinders are much less accurate. Although some beakers have
graduations on the side, the graduations are only useful to give very approximate indications of
volume.
For colourless gases that are also less dense than air, we collect over water because if we use
upwards delivery downwards displacement we won’t know when all gas collected
heat evolved causing the glass to break was a common answer. The suggested improved was
often to use Pyrex glass to withstand high temperatures
Larger volumes like 250 cm3 we use volumetric flasks
When mixing something that has already been dissolved we do so to allow for an even/ uniform
concentration throughout the liquid
When “transferring liquid” from a volumetric flask to conical flask during titration make use of
graduated pipette
Best titration result within 0.2 cm3 of each other - concordant results
Conical flask = Erlenmeyer Flask
Sulfur dioxide contains sulfite ions SO3 2Using glass beaker in experiments where temperature are being measured - allows heat loss
therefore should use plastic cup/ polystyrene cup
organic liquids / alcohol / alkene flammable + do not have flames / lighted Bunsen
acid corrosive + wear goggles
State what the student does to the cathode after removing it from the solution but before placing
it on the balance to measure its mass.- wash with distilled water and dry
In apparatus like this we START reaction by tipping/shaking conical flasks so acid and copper
carbonate come in contact.
We don’t directly add copper carbonate and then place bung because want to avoid any loss of
gas → more accurate results
This is a BOILING TUBE thicker than test tube
When transferring washings (remaining solution left in pipette) we wash with distilled water
OTHERWISE when using an apparatus to TRANSFER particular solution we use that soution
to wash apparatus