CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Three test tubes (X, Y, and Z) contain equal total volumes of liquid water. A magnified particulate-level drawing of each tube is described below.
• Tube X: 8 identical solute particles are dispersed among 40 water molecules.
• Tube Y: 6 identical solute particles are dispersed among 30 water molecules.
• Tube Z: 10 identical solute particles are dispersed among 70 water molecules.
Respond to the prompts about the relative solution concentrations.
(1) Part 1: (a) Order the test tubes from most concentrated to least concentrated, explaining your reasoning in terms of the ratio of solute particles to water molecules.
(2) Part 2: (b) Suppose 20 additional water molecules are added to tube X while no solute is added or removed. State whether the concentration in tube X increases, decreases, or remains the same, and justify your answer.
(3) Part 3: (c) In tube Y the solute is CaCl2, which dissociates completely into ions when dissolved. Re-evaluate your ranking from part (a) if the comparison is based on the total number of dissolved ions rather than the number of formula units, and explain any changes.