A student is given the balanced molecular equation for the decomposition of solid…
CHEMISTRY · Multi-part · AP · Chemistry · Chemical Reactions · Chemical Reactions
Problem
A student is given the balanced molecular equation for the decomposition of solid ammonium dichromate:
(NH4)2Cr2O7(s) → Cr2O3(s) + N2(g) + 4 H2O(g)
Three different particulate diagrams have been proposed to depict one microscopic event corresponding to the complete decomposition of a single formula unit of (NH4)2Cr2O7.
Diagram I shows: 2 green spheres bonded together (Cr2), 7 red spheres not bonded (O atoms), 2 blue spheres bonded (N2), and 8 white spheres bonded in 4 pairs (H2).
Diagram II shows: 1 green sphere and 1 green sphere bonded to 3 red spheres total (Cr2O3 unit), 2 blue spheres bonded (N2), and four separate clusters each containing two white spheres and one red sphere (H2O units).
Diagram III shows: 1 cluster of two green spheres bonded to three red spheres (Cr2O3), 1 pair of blue spheres (N2), and 4 separate clusters each composed of two white spheres and one red sphere (H2O).
Assume the colors correspond to the following atom key: green = Cr, red = O, blue = N, white = H.
Determine which diagram(s), if any, correctly represent the reaction at the particulate level.
(a) For each diagram, tally the number of atoms of every element present.
(b) Compare each tally with the stoichiometry of the balanced equation to decide whether the diagram is consistent with both mass conservation and correct product formulas.
(c) Identify all diagrams that are fully consistent with the balanced equation and justify your selections in terms of both atom counts and chemical identity of the species depicted.