CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A teacher distributes two 50 mL beakers, each containing water at 25 °C, to a lab group. The students add exactly 0.20 g of solid calcium chloride, CaCl₂, to Beaker 1 and exactly 0.20 g of solid sucrose, C₁₂H₂₂O₁₁, to Beaker 2, stirring until each solute dissolves completely. Assume CaCl₂ dissociates fully while sucrose remains as intact molecules.
(a) Calculate the number of formula units (or molecules) of solute added to each beaker. Show your work, including molar masses and any constants used.
(b) For Beaker 1, determine the total number of individual solute particles present after dissolution, counting each ion separately.
(c) The students will sketch a single, equal-volume box for each beaker. Propose a particle-count scheme (number of solute particles and an approximate but reasonable number of solvent molecules) that would proportionally reflect the particle ratios you obtained in parts (a) and (b), while keeping each diagram to 20 or fewer solute particles. Explain how your chosen numbers preserve the relative composition.
(d) Explain how the orientation of water molecules around solute particles should differ between the two diagrams, citing the dominant intermolecular interactions in each case.