When ammonia is added to a copper(II) sulfate solution, the pale blue Cu²⁺(aq) ion is progressively replaced by the deep blue tetraamminecopper(II) complex [Cu(NH₃)₄]²⁺. The intensity of this colour change can be measured precisely using a colorimeter, and the relationship between ammonia concentration and absorbance reveals the stepwise nature of complex ion formation. This makes it a visually dramatic and analytically rich IB Chemistry HL IA. This practical is suitable for IB Diploma Chemistry HL.

In this investigation, you will measure the electromotive force (EMF) of a simple electrochemical cell as you systematically vary the concentration of one electrolyte. By applying the Nernst equation, you can derive a linear relationship between EMF and the logarithm of concentration, allowing you to calculate fundamental thermodynamic quantities. This is one of the most analytically powerful IB Chemistry HL Internal Assessment topics available.

Aspirin (acetylsalicylic acid) undergoes hydrolysis in aqueous solution to produce salicylic acid and ethanoic acid. The rate of this hydrolysis is strongly dependent on pH. In this investigation, you will use a colorimeter to track the appearance of salicylate ions (which form a purple complex with iron(III) ions) and measure how pH affects the rate of hydrolysis. This produces a fully continuous dataset in both IV and DV, making it an outstanding IB Chemistry IA.

Vitamin C (ascorbic acid, C₆H₈O₆) is an essential nutrient and a reducing agent that is readily oxidised. In this investigation, you will use iodometric titration to measure the vitamin C content of fruit juice after exposure to two continuous variables: temperature and metal ion concentration. Both investigations use the same titration method, making this a versatile and highly scorable IB Chemistry IA topic. This practical is suitable for IB Diploma Chemistry and makes an excellent Internal Assessment (IA) topic.