Practicals

Question 1

Make a standard solution

Answer 1

1. Weigh out accurate mass of solid in clean, dry beaker
2. Add enough distilled water to dissolve the solid, stirring with a glass rod
3. Transfer the solution with rinsing to a 250cm3 volumetric flask using a funnel
4. Rinse beaker and glass rod and add rinsings to flask
5. Make up to the mark with distilled water until bottom of meniscus is on the line
6. Stopper the flask and invert to mix thoroughly

Question 2

Perform a titration

Answer 2

1. Rinse the burette with the solution you intead to fill it with. Discard rinsings and fill burette.
2. Rinse a popette with the solution you are going to put in it. Discard rinsings and use a glass pipette and pipette filler to transfer 25cm3 of the solution into the conical flask.
3. Add 2 to 3 drops of suitable indicator to the conical flask
4. Add solution from the burette, with constant swirling, until the indicator just changes colour. This is a trial titration.
5. Repeat the titration, adding dropwise near the end point, until 2 to 3 concordant results have been achieved
6. Calculate mean titre from concordant results

Question 3

Determine enthalpy of combustion

Answer 3

1. Measure 100cm3 of water into a calorimeter
2. Weigh a spirit burner containing the liquid to be burnt
3. Measure the intial temp of the water with a thermometer
4. Use the spirit burner to heat the water
5. Stop heating after reasonable temp rise (10/15c). Stir and measure exact final temp.
6. Reweigh spirit burner
7. Calculate temp change and heat energy change (q=mc x change in T)
8. Calculate no of moles burnt
9. Calculate energy change per mole

Question 4

Determine enthalpy change of neutralisation

Answer 4

1. Place a polystyreme cup in a glass beaker for support
2. Rinse a measuring cylinder with an acid and then measire 25cm3 of this acid and transfer to polystyrene cup
3. Stir acid with thermometer and record temp
4. Rinse a second measuring cylinder with a base and the measure 25cm3 of the base
5. Add the base to the acid, stir and record the highest temp reached
6. Calculate temp change and heat energy change (q=mc x change in T)
7. Use a balanced symbol equation to calculate the no of mols of water formed and then calculate energy change per mole

Question 5

Determining how rate of reaction changes with temp

Answer 5

1. Mix solutions in a flask and place over a piece of paper with a black cross on
2. Start timer
3. Record the time it takes for cross to be no longer visable due to precipitate

Alternatively, measure rate of gas production using gas syringe or change in mass over time