CHEMISTRY · Multi-part · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
A student prepares four sealed 50 mL vials (A–D), each of which contains a different sample at 25 °C.
• Vial A: 15 mL of distilled water in which exactly 2.00 g of NaCl has been dissolved with vigorous stirring until no solid remains visible.
• Vial B: 15 mL of river water collected immediately after a rainstorm; under normal lighting the sample appears cloudy and small solid particles can be seen with the naked eye.
• Vial C: 15 mL of commercial vegetable oil purchased from a grocery store; no other substances are added.
• Vial D: A physical mixture consisting of 5.00 g of copper turnings and 5.00 g of zinc turnings, placed together in the vial.
Assume all samples are at equilibrium and no chemical reactions occur among components.
(a) For each vial (A–D) classify the sample as a homogeneous mixture, a heterogeneous mixture, or not a mixture at all. Provide a brief justification for every classification that explicitly refers to the macroscopic distribution of observable properties.
(b) Choose ONE of the four vials and design a simple, practical test (that could be carried out in a high-school laboratory) to experimentally verify your classification for that vial. Describe the procedure and identify the specific observations that would confirm your conclusion.
(c) Suppose the student vigorously shakes Vial B and lets it stand undisturbed for 48 h. Predict whether the appearance of the sample after 48 h would strengthen, weaken, or have no effect on your original classification of Vial B. Justify your prediction.