required practicals Flashcards
1
Q
what is the method of making a salt?
A
- pick the right acid (sulphuric acid ) and a soluble base (copper oxide)
- gently warm acid DO NOT BOIL
- add the copper oxide to the base until it is in excess
- filter out the excess solid to get the salt solution
- to get pure crystals, gently heat solution in water bath to get evaporation going and then leave on window to crystallise
- wipe with paper towl to get rid of any water left
2
Q
explain the method for titrations
A
- put the alkali in a conical flask using a pipette, then add two or three drops of indicator (phenolphthalein)
- use a funnel to fill the burette with some acid of a known concentration, making sure you do it BELOW EYE LEVEL to prevent it falling in your eye and record the initial volume of acid in the burette (use the meniscus)
- slowly add the acid to the alkali a bit at a time giving the conical flask a regular swirl
- the indicator changed colour when it it fully neutralised
- record final volume of acid in the burette and then work out the volume of acid used to neutralise the alkali
3
Q
explain the method for electrolysis
A
place the two carbon electrodes (that are inert -can’t react) in the beaker with the electrolyte in and turn the power supply on
4
Q
explain the practice for exothermic and endothermic reactions
A
- put 25cm cubed of 0.25 mol/dm cubed of hydrochloride acid and sodium hydroxide in separate beakers
- place the beakers in a water bath sothat they are at the same temp (25 degrees celsius)
- add the HCl and NaOH to the polystyrene cup with the lid and take the temp very 30 secs
- repeat these steps using 0.5 mol/dm cubed and then 1mol/dm cubed of HCl
