1972 Ap Chemistry Free Exclusive Response Answers 🆕 Real

1972 AP Chemistry Free Response: Solutions and Analysis

Add hot water

to the precipitate → PbCl₂ is slightly soluble in hot water; AgCl is not. Decant hot solution and cool → PbCl₂ recrystallizes (white needles). Confirm Pb²⁺ with 1M H2SO4 → white PbSO₄ precipitate.

Answer Guide:

• Net ionic: ( [Ag(NH_3)_2]^+ + Cl^- + 2H^+ → AgCl(s) + 2NH_4^+ )

[ \Delta H^\circ_rxn = \sum \Delta H_f^\circ (\textproducts) - \sum \Delta H_f^\circ (\textreactants) ] [ = [2(-94.1) + 1(-68.3)] - [1(+54.2) + \frac52(0)] ] [ = [-188.2 - 68.3] - [54.2] ] [ = -256.5 - 54.2 = -310.7 , \textkcal/mol ] 1972 ap chemistry free response answers

1. Stoichiometry & limiting reactant
2. Gas laws and kinetic molecular theory
3. Thermochemistry (enthalpy, heats of reaction, calorimetry)
4. Chemical equilibrium (K, Le Chatelier)
5. Acid–base theory and pH calculations
6. Electrochemistry (cells, standard potentials)
7. Reaction kinetics (rate laws, order, activation energy)
8. Atomic structure & spectra / periodic trends
9. Qualitative analysis and lab technique (titration, precipitation)
10. Organic functional groups and simple reactions (naming, basic mechanisms)