Two clear, colorless aqueous solutions—Solution A and Solution B—are each at an…
CHEMISTRY · Multi-part · AP · Chemistry · Chemical Reactions · Chemical Reactions
Problem
Two clear, colorless aqueous solutions—Solution A and Solution B—are each at an initial temperature of 25∘C. When 50 mL of Solution A is mixed with 50 mL of Solution B in a coffee-cup calorimeter, the temperature of the mixture rises steadily to 47∘C and vigorous effervescence (rapid bubbling) is observed for about 30 s before the solution becomes still.
Assume that no heat is lost to the surroundings and that the specific heat capacity and density of each solution are identical to those of liquid water.
(a) Identify every piece of macroscopic evidence in the scenario that could suggest the occurrence of a chemical change.
(b) Calculate the numerical value of the temperature change for the mixture.
(c) Explain whether the observed temperature change, by itself, is sufficient proof that a chemical change has occurred. Include reasoning that considers both chemical and physical possibilities.
(d) Propose one additional, feasible experimental test (other than temperature measurement) that could be performed on the final mixture to provide further confirmation of a chemical change, and justify how the results would be interpreted.