A laboratory technician is given an unlabeled blue crystalline solid that may be…
CHEMISTRY · Multi-part · CBSE · Chemistry · Acids, Bases and Salts · Acids, Bases and Salts
Problem
A laboratory technician is given an unlabeled blue crystalline solid that may be either solid CuSO4 • 5 H2O or a mixture of anhydrous CuSO4(s) and NaCl(s). Only small-scale apparatus (test tubes, beakers, Bunsen burner, balance, and simple glassware) is available.
Design and justify an experimental procedure that allows the technician to determine whether heating the sample to 150 °C results in a physical change, a chemical change, or both.
(1) Outline a step-by-step experimental procedure (including observations to be recorded) that distinguishes among the following possibilities after heating:
(i) The blue solid undergoes only loss of water of hydration.
(ii) The blue solid undergoes a decomposition of the sulfate salt.
(iii) The sample is a mixture in which NaCl remains unchanged while CuSO4 • 5 H2O loses water.
(2) For each possible outcome in part (a), predict the macroscopic observations (color changes, mass changes, appearance of vapors, etc.) that would serve as evidence.
(3) Explain, using particulate-level reasoning, why the observations you listed in part (b) allow classification of each outcome as a physical change, a chemical change, or a combination of the two.