Required practical 1: making a volumetric solution and carrying out a simple acid and base titration

Required practical 1: making a volumetric solution and carrying out a simple acid and base titration

Describe the steps to make a standard solution

• add solid, record difference in mass of weighing boat

• Add distilled water to the beaker and stir with a glass rod

• Pour into volumetric flask with funnel

• Make up total volume with distilled water

• Invert flask several times to ensure a uniform solution

Describe the steps to make a titration

• make sure jet safe is filled and note brunette reading before and after adding an acid (or alkali)

• Add solution from beretta with occasional swirling, add drop wise near the end point

• Repeat experiment to get concordant results, work out average titre

(For titration) Why can you distilled water to the conical flask?

• washes the sides of the flask so that all of the acid is adding into the mixture and it doesn’t change the number of moles

Why would you use a volumetric pipette rather than a measuring cylinder?

-more accurate due to having a smaller uncertainty

(For titration) Why would you rinse the burette with acid?

• you don’t want to dilute the mixture because concentration will decrease

Why shouldn’t you leave a funnel in the burette

• small drops of liquid may fall and give a false reading

Why should you use a white tile under the conical flask?

• observes colour change

How do you reduce uncertainty?

• use a pipette instead

• Make the titre a larger volume by increasing concentration of substance in conical flask

What would you use to decrease uncertainty of an apparatus?

• use an apparatus with finer scale divisions

• Use a more accurate mass balance

• Use larger mass

(Manganate titration) Why should you only use sulfuric acid?

• some acids set up alternative redox reactions

(Manganate titration) What happens if you use a weak acid or insufficient volume?

• MnO2 produced instead of Mn2+ (less H+ ions) which masks the colour change

(Manganate titration) Why can’t you use HCL?

• CL- ions are oxidised to Cl2 by MnO4- so greater volume of Manganate used

(Manganate titration) Why shouldn’t we use nitric acid?

• nitric acid acts as an oxidising agent so oxidised Fe2+ to Fe3+ so smaller volume of Manganate used