AP Chemistry Enthalpy Review for Before Entropy and Gibbs Energy Name ______

AP Chemistry Enthalpy Review for before Entropy and Gibbs Energy Name ______

1. Predict which of the following spontaneous reactions are exothermic and which are endothermic: a. H2O(l) → H2O(g) b. 2Mg(s) + O2(g) → 2MgO(s)

c. Ba(OH)28H2O(s) + 2NH4Cl(s) → BaCl2(aq) + 10H2O(l) + 2NH3(aq) d. H2(g) + O2(g) → H2O(l) e. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) f. Al(s) + Br2(l) →AlBr3(s) 2. The natural tendency for spontaneous chemical reactions is to release heat. Is the enthalpy alone a good predictor of spontaneity? Explain. 3. Using the partial chart of Thermodynamic Values on the back, calculate the enthalpy change for each of the reactions in a-f above.

AP Chemistry Entropy WS 1. Define entropy: 2. Predict which of the following spontaneous reactions have an increase in entropy (mark as “+”) and which have a decrease in entropy (mark as “-“). a. H2O(l) → H2O(g) b. 2Mg(s) + O2(g) → 2MgO(s)

c. Ba(OH)28H2O(s) + 2NH4Cl(s) → BaCl2(aq) + 10H2O(l) + 2NH3(aq) d. H2(g) + O2(g) → H2O(l) e. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) f. Al(s) + Br2(l) →AlBr3(s) 3. What is the label difference between entropy and enthalpy? Explain (discuss both parts). 4. What is the sign difference (like + and -) between entropy and enthalpy? Explain (discuss both parts). 5. The natural tendency for spontaneous chemical reactions is to increase entropy. Is the entropy alone a good predictor of spontaneity? Explain. 6. Using the partial chart of Thermodynamic Values on the back, calculate the entropy change for each of the reactions in a-f above.

AP Chemistry Gibbs Energy WS 1 1. What are the two meanings of the signs (+ and -) of ΔG? 2. All of the following are spontaneous reactions. State which factor, enthalpy or entropy, played the biggest part. It might help to make a chart of the signs of enthalpy and entropy to see what made Gibbs energy negative. a. H2O(l) → H2O(g) b. 2Mg(s) + O2(g) → 2MgO(s)

c. Ba(OH)28H2O(s) + 2NH4Cl(s) → BaCl2(aq) + 10H2O(l) + 2NH3(aq) d. H2(g) + O2(g) → H2O(l) e. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) f. Al(s) + Br2(l) →AlBr3(s) 3. Using the partial chart of Thermodynamic Values on the back, calculate the Gibbs energy change for each of the reactions in a-f above. (Do NOT use your answers from the first two problem sets, in case they are incorrect.)