IB Chemistry IA idea · Analysis, colour and spectroscopy
IB Chemistry IA idea: how much iron can acid extract from cereal?
A cereal box lists iron; test how much your stomach's acid might free.
These ideas are starting points, not an IA to copy. Never copy an idea blindly: make the question, method and analysis your own, and check your plan with your teacher.
Example research question
How does the concentration of hydrochloric acid used to extract iron from fortified cereal (0.01, 0.05, 0.1, 0.5 and 1.0 mol dm⁻³) affect iron extracted (mg per 100 g), from the red iron(III) thiocyanate absorbance?
Change the system, the range or the method so the question is yours. Check it against the research question checklist in our Chemistry IA guide.
Variables
- You change
- Concentration of hydrochloric acid used to extract the iron, 0.01 to 1.0 mol dm-3 (5 or more values)
- You measure
- Iron extracted (mg per 100 g cereal), from the red absorbance of iron(III) thiocyanate against a calibration
- You keep the same
- Mass and fineness of cereal
- Volume and time of extraction
- Wavelength
- Oxidation of iron(II) to iron(III) before colour development
Method
Grind cereal, extract in dilute acid for a fixed time, filter, oxidise iron(II) with a drop of hydrogen peroxide, develop the red colour with thiocyanate and read absorbance.
Data analysis
Build a calibration with iron(III) standards; calculate extracted iron; plot against acid concentration; compare with the label; propagate uncertainty.
How it works
You change Extraction acid (mol dm⁻³) and measure Iron extracted (mg per 100 g) in Ground fortified cereal, keeping Cereal mass, Extraction time, Cereal brand the same. Expect a graph of Iron extracted / mg per 100 g against HCl concentration / mol dm⁻³: Extra acid helps, then adds little.
Make it yours
Test extraction at 37 degrees C or compare cereals.
Extended Essay angle
Develop and validate a complete analytical method with spike recovery and detection limits.
Safety
Take care with: hazardous chemicals.
Dilute acid and thiocyanate solutions irritate; keep the acid dilute and cold; eye protection.
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