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CORE PRACTICALs
CP1: making up a solution (p1)
1. Weigh the sample bottle containing the solid on a (2 dp) balance.
2. Transfer solid to beaker and reweigh sample bottle.
3. Record the difference in mass.
4. Add distilled water and stir with a glass rod until all the solid has dissolved.
5. Transfer to a volumetric flask with washings.
6. Make up to the 250cm3 mark with distilled water.
7. Shake flask.
Reducing uncertainties in measuring mass:
● Using a more accurate balance or a larger mass will reduce the uncertainty
in weighing a solid.
CP1: titration (p2)
1. rinse the burrete with the NAOH because distilled water will change the
concetration/moles of the acid
2. FIll the burrette with sodium hydroxide solution
3. use a volumetric pipette to transfer 25cm3 of the citric acid solution into the
conical flask.
Use a pipette not a measuring cylinder because it has a smaller uncertainty.
distilled water on the sides of the conical flaks to ensure all reactants are in the
mixture
Use a conical falsk because its easier to swirl
4. Add a few drops of the indicator
To much can change the colour so the titre wouldnt be accurate
CORE PRACTICALs 1
, 5. add the sodium hydroxide solution from the burette into the conical flask
and swirl continuously
not constantly swirling means that it hasnt fully reacted so it changes the
endpoint so swirl until a permanent colour change
6. repeat tiration to get concordant results
Remove the funnel because drops from the funnel enetrs he burette which
could increase the volume
reduce percentage uncertainty by using a larger mass of a solid or latger
concentration of solution and this incraeses the titre volume
CP2: Enthalpy change
1. use a burette/pipette to meaure acid insteda of the measuring cylinder
2. use a polystrene cup to insulate the sides of the cylinder
3. meausre the acid and record the teperature of the soultion before and after
addition at regular intervals
4. plot a graph with teperayure agaisnt time
5. extrapolate the graph to the point of addition to determine temperature
cahnge
% uncertainty can be reduced by ncreasing the conc of the sol and stirring so
the temperature is evenly distriuted
pressure needs to be ocnstant for the haet change calculation
Experimental is different to the theoretical;
heat loss to the appartus
incomplete combustion
non standard conditions
evaporaion of waterr/ alcohol
CP3- Rate of reaction experiment
initail rates
CORE PRACTICALs 2
, AIM: To measure the rate of reaction by timing how long it takes for a visible
change (disappearance of a cross) to occur.
Steps:
1. Mix sodium thiosulfate (Na₂S₂O₃) with hydrochloric acid (HCl) in a beaker
placed over a cross drawn on paper.
2. Reaction:
Na₂S₂O₃ + 2HCl → 2NaCl + SO₂ + S↓
(Produces a cloudy precipitate of sulfur.)
3. Start the stopwatch as soon as you mix the reactants.
4. Time how long it takes for the cross underneath to disappear.
5. Repeat the experiment at 5 different temperatures.
6. Plot a time vs amount of sulfur graph; the gradient = rate.
7. Then plot a rate vs temperature graph.
Controls:
Keep concentrations of reactants the same.
Keep volume of all solutions the same.
Use the same beaker and same cross underneath each time.
Use one person to judge when the cross disappears to reduce subjectivity.
Continous monitoring method
Aim: To measure the rate of reaction by recording gas volume produced over
time.
Steps:
1. Set up a reaction that produces a gas (e.g. magnesium with hydrochloric
acid).
2. Use a gas syringe or inverted measuring cylinder to collect the gas.
3. Start timing when the reactants are mixed.
4. Record the volume of gas at regular time intervals (e.g. every 10 seconds).
CORE PRACTICALs 3
CORE PRACTICALs
CP1: making up a solution (p1)
1. Weigh the sample bottle containing the solid on a (2 dp) balance.
2. Transfer solid to beaker and reweigh sample bottle.
3. Record the difference in mass.
4. Add distilled water and stir with a glass rod until all the solid has dissolved.
5. Transfer to a volumetric flask with washings.
6. Make up to the 250cm3 mark with distilled water.
7. Shake flask.
Reducing uncertainties in measuring mass:
● Using a more accurate balance or a larger mass will reduce the uncertainty
in weighing a solid.
CP1: titration (p2)
1. rinse the burrete with the NAOH because distilled water will change the
concetration/moles of the acid
2. FIll the burrette with sodium hydroxide solution
3. use a volumetric pipette to transfer 25cm3 of the citric acid solution into the
conical flask.
Use a pipette not a measuring cylinder because it has a smaller uncertainty.
distilled water on the sides of the conical flaks to ensure all reactants are in the
mixture
Use a conical falsk because its easier to swirl
4. Add a few drops of the indicator
To much can change the colour so the titre wouldnt be accurate
CORE PRACTICALs 1
, 5. add the sodium hydroxide solution from the burette into the conical flask
and swirl continuously
not constantly swirling means that it hasnt fully reacted so it changes the
endpoint so swirl until a permanent colour change
6. repeat tiration to get concordant results
Remove the funnel because drops from the funnel enetrs he burette which
could increase the volume
reduce percentage uncertainty by using a larger mass of a solid or latger
concentration of solution and this incraeses the titre volume
CP2: Enthalpy change
1. use a burette/pipette to meaure acid insteda of the measuring cylinder
2. use a polystrene cup to insulate the sides of the cylinder
3. meausre the acid and record the teperature of the soultion before and after
addition at regular intervals
4. plot a graph with teperayure agaisnt time
5. extrapolate the graph to the point of addition to determine temperature
cahnge
% uncertainty can be reduced by ncreasing the conc of the sol and stirring so
the temperature is evenly distriuted
pressure needs to be ocnstant for the haet change calculation
Experimental is different to the theoretical;
heat loss to the appartus
incomplete combustion
non standard conditions
evaporaion of waterr/ alcohol
CP3- Rate of reaction experiment
initail rates
CORE PRACTICALs 2
, AIM: To measure the rate of reaction by timing how long it takes for a visible
change (disappearance of a cross) to occur.
Steps:
1. Mix sodium thiosulfate (Na₂S₂O₃) with hydrochloric acid (HCl) in a beaker
placed over a cross drawn on paper.
2. Reaction:
Na₂S₂O₃ + 2HCl → 2NaCl + SO₂ + S↓
(Produces a cloudy precipitate of sulfur.)
3. Start the stopwatch as soon as you mix the reactants.
4. Time how long it takes for the cross underneath to disappear.
5. Repeat the experiment at 5 different temperatures.
6. Plot a time vs amount of sulfur graph; the gradient = rate.
7. Then plot a rate vs temperature graph.
Controls:
Keep concentrations of reactants the same.
Keep volume of all solutions the same.
Use the same beaker and same cross underneath each time.
Use one person to judge when the cross disappears to reduce subjectivity.
Continous monitoring method
Aim: To measure the rate of reaction by recording gas volume produced over
time.
Steps:
1. Set up a reaction that produces a gas (e.g. magnesium with hydrochloric
acid).
2. Use a gas syringe or inverted measuring cylinder to collect the gas.
3. Start timing when the reactants are mixed.
4. Record the volume of gas at regular time intervals (e.g. every 10 seconds).
CORE PRACTICALs 3
