Practicals Flashcards
1
Q
Standard Solution
A
- accurately weight out a dry sample of solid using a high precision balance
- transfer to a beaker and freeing the weighing boat to determine mass transferred
- dissolve acid in a small volume of distilled water, stirring with a glass rod
- transfer to volumetric flask
- add deionised water up to calibration line
- ensure meniscus rests on calibration line
- stopper bottle and invert 10 times to homogenise the solution
2
Q
Acid-Base Titration
A
_____ = any substance
- rinse the burgers with whatever is going in the burette to remove any contamination (can’t use water because there will be water left behind which will dilute whatever is in burette)
- overfill burette with _____ and run through so jet space is filled/ remove air
- use volumetric pipette to transfer 25cm3 of (other thing tittering) to a conical flask (we use conical flask to avoid any splashing during titration)
- add 2 drops of suitable indicator e.g. phenolphthalein
- slowly add contents inside burette
- swirl between additions
- rinse burette and sides of conical flask with wash bottle
- stop at first permanent colour change and reduce volume of contents inside burette
- repeat titrations until concordant data achieved and use concordant data to calculate mean titre
- use n=cv to calculate moles of whatever added
3
Q
Measuring Enthalpy change of a reaction
A
_____ = any substance
- measure _cm^3 of water using a burette/pipette (not measuring cylinder because that adds error)
- transfer to polystyrene cup with lid
- measure 4g of ____ using an accurate balance
- use a thermometer to take the temperature of the water each minute for 2-3 minutes to establish an accurate initial temperature
- pour the copper surface into the water at minute 4
- reweigh the weighing boat again to find the correct mass of _____ transferred
- stir solution
- continue to record the temperature at minute intervals up to 15 minutes
- plot a temperature against time graph
- extrapolate back to point of addition and determine temperature change
4
Q
Distillation
A
_____ = any substance
- transfer reaction to a round-bottomed flask
- add anti bumping granules (to create smaller bubbles)
- clamp round-bottomed flask over electric heater (safer than naked flame cuz alcohol flammable )
- add bung with integrated thermometer, which sits at height of side-arm
- ensure bung fully seals flask to allow collection of ____
- attach condenser - water should enter at the bottom and leave through top
- apply heat
- collect the distillate from beaker within ice bath when thermometer shows boiling point of ____
5
Q
Iodine Clock (initial rate of reaction)
A
- perform a series of experiments in which only the concentration of solution A varies
- add 5cm^3 of solution B and 1cm^3 of starch to a beaker
- simultaneously add 5cm^3 of solution A and start timer
- record time taken for blue colour change to appear
- dilute solution A so concentration is half original
- repeat experiment and record time taken
- use 1/time taken for blue to appear
- if rate x2 when [A] x2, 1st order if rate does not change then zero order or x4 then 2nd order etc
6
Q
Continuous monitoring of rate of reaction (gas syringe one)
A
_____ = any substance
- Use a burette to measure 50cm^3 of ____ (likely hydrogen peroxide) into a conical flask
- use a high precision balance to measure 1g of manganese dioxide (aka the catalyst, this is significantly in excess so concentration is effectively unchanging)
- prepare bung with delivery tube attached to gas syringe
- add catalyst to flask, insert bung and start stop watch
- record volume of gas released every 10 seconds until syringe is full
- calculate concentration remaining for each time point
- plot concentration against time
- draw tangents at each time poking to establish rate for each concentration
- plot a rate-concentration graph and identity the order
7
Q
REFLUX DIAGRAM
A
8
Q
Why is a water bath used during heating of a reaction mixture rather than a bunsen burner flame?
A
Water Bath is needed because a reaction mixture is composed of reactants that are flammable.
