Required Practicals

Question 1

RP1 - Method for making a standard solution

Answer 1

• Weigh out an accurate mass of solid into a clean, dry beaker
• Add enough deionised water to dissolve the solid, stirring with a glass rod
• Transfer the solution with rinsing to a 250cm³ volumetric flask using a funnel
• Rinse the beaker and glass rod with deionised water and add to the volumetric flask
• Make up to the mark by adding deionised water until the bottom of the meniscus is on the mark
• Stopper the flask and invert to mix thoroughly

Question 2

RP1 - Percentage error calculation

Answer 2

(uncertainty/quantity measured) x 100

Question 3

RP1 - Method for standard titration

Answer 3

• Rinse the burette with the solution you are going to fill it with
• Discard the rinsings and fill the burette
• Rinse the pipette with the solution you are going to pipette into the conical flask
• Using a pipette and pipette filler, transfer 25cm³ of this solution into a conical flask
• Add 2-3 drops of suitable indicator
• Add the solution from the burette, with constant swirling until the indicator changes colour. This is a trial titration.
• Repeat the titration to achieve 2-3 concordant results, adding drop wise near the end point
• Calculate the mean titre from the concordant results

Question 4

RP1- Give two indicators used in titrations

Answer 4

Methyl orange:
Acid = Red
Alkali = Yellow
Ideal for = Strong acid-strong base or weak acid-strong base

Phenolphthalein:
Acid = Colourless
Alkali = Pink
Ideal for = Strong acid-strong base or weak acid-strong base

Question 5

RP2 - Method for determining the enthalpy of combustion of a fuel

Answer 5

• Accurately measure 100cm³ of water into a calorimeter (100cm³ is the same as 100g water)
• Weigh a spirit burner containing the liquid to be burned
• Measure the initial temperature of the water using a thermometer
• Use the spirit burner to heat the water
• Stop heating when there is a reasonable temperature rise
• Stir and measure the final temperature of the water using a thermometer
• Reweigh the spirit burner
• Calculate the temperature change and heat energy change
• Calculate the mass of fuel used up and therefore the number of moles
• Calculate the energy change per mole of fuel

Question 6

RP3 - Method for investigating how the rate of reaction changes with temperature

Answer 6

• Place a conical flask on top of a piece of paper with a cross on
• Add 25cm