You can explore the enthalpy of precipitation of Lead halides for the IB chemistry internal assessment. This can be a good IA based on hands on experiment. In this IA you need to explore the precipitation of different lead halides from group 7 halogens. You can measure the enthalpy change during the precipitation of each lead halide and compare them.
The enthalpy of precipitation of Lead halides describes the amount of energy released when these particular compounds form a solid precipitate. Lead halides consist of lead ions (Pb2+) and either chloride, bromide, or iodide ions (X). When an aqueous solution containing lead nitrate and one of these various halide ions is mixed, a precipitation reaction occurs resulting in solid PbX2. This reaction can be represented as Pb(NO3)2 (aq) + X (aq) → PbX2 (s) + 2NO3 (aq). The amount of energy released during this process is referred to as the lattice energy and is strongly related to the electrostatic forces that exist between the ions in the crystal structure. To measure this energy value, calorimetry can be used to determine the heat absorbed or released during the reaction.
The enthalpy of precipitation is the heat energy change when a lead halide (PbX2) precipitate forms from an aqueous solution of lead nitrate (Pb(NO3)2) and other halide ions (Cl-, Br-, or I-). The formation of a solid precipitate releases the lattice energy in the form of thermal energy, which is related to the electrostatic forces between ions. In order for precipitation to occur, the solubility product constant (Ksp) must be exceeded, and lead halides have relatively low Ksp values. Hence, they form stable compounds with relatively high lattice energies. To measure the enthalpy of precipitation accurately, calorimeters are used to determine heat absorbance/release during the reaction.
The enthalpy of precipitation is an energy change that occurs when a solid precipitate forms in an aqueous solution. Lead halides, including chloride, bromide and iodide, are composed of lead ions and halide ions. Upon combining lead nitrate with the halide ion (cl-, br-, or i-), they form a solid lead halide precipitate according to the equation
Pb(NO3)2 (aq)+ X(aq) → PbX2(s) + 2NO3 (aq).
The reaction has a related enthalpy change, which can be measured with a calorimeter to determine how much heat is absorbed or released during the process. This energy release is due to the lattice energy required to separate the ions in a crystal lattice which has been determined by the electrostatic forces between them.
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