Determination of the amount (%) of iron in an iron tablet Flashcards
Apparatus needed
PESTLE AND MORTAR, safety glasses, clock glass, funnel, balance, beaker, stirrer, pipette, burette, 250cm³ volumetric flask, retort stand, conical flask, wash bottle with deionised water, white tile.
Material needed
Irons tablets, dilute sulphuric acid, standard solution of KMnO₄ (0.02M).
Why should this experiment get done ASAP?
As KMnO₄ concentration will continue to change as it is not stable in air, if we leave it for a period of time our results for the next experiment will not be accurate.
Is KMnO₄ a primary or a secondary standard?
Secondary
Why is KMnO₄ a secondary standard?
As it is not stable in air.
What is the first step in the method?
5 iron tablets were weighed accurately on a clock glass using a balance.
What was the mass of the 5 tablets when they were placed on the clock glass?
1.56g
What happens after the iron tablets were weighed?
The tablets were crushed using a pestle and mortar with some dilute sulphuric acid.
Why were the tablets crushed using a pestle and mortar with some dilute sulphuric acid?
To prevent aerial oxidation of the iron (II) in the tablets and to dissolve the tablets more quickly.
What happens after the tablets were crushed using a pestle and mortar with some dilute sulphuric acid?
This paste was then transferred to a 250cm³ volumetric flask using a funnel.
What happens after the paste was transferred to a 250cm³ volumetric flask using a funnel?
The pestle and mortar and funnel were washed several times with deionised water and the rinsings were added to the volumetric flask.
What happens after the pestle and mortar and funnel were washed several times with deionised water and the rinsings were added to the volumetric flask?
The solution was then made up to 250cm³ observing the usual precautions.
What happens after the solution was then made up to 250cm³ observing the usual precautions?
The pipette was washed with deionised water and some of the solution and then 25cm³ of this solution were transferred to a clean conical flask observing the usual safety precautions.
What happens after the pipette was washed with deionised water and some of the solution?
Roughly 20cm³ of dilute sulphuric acid was added to the solution in the conical flask.
Why was roughly 20cm³ of dilute sulphuric acid was added to the solution in the conical flask?
To ensure complete reduction of Mn(+7) to Mn(+2).
