chem 3 test sample questions

Determine ΔG°rxn using the following information. FeO(s) + CO(g) → Fe(s) + CO2(g) ΔH°= -11.0 kJ; ΔS°= -17.4 J/K +1.6 kJ +191.0 kJ -6.4 kJ -5.8 kJ +89.5 kJ

-5.8 kJ

Estimate ΔG°rxn for the following reaction at 387 K. HCN(g) + 2 H2(g) → CH3NH2(g) ΔH°= -158.0 kJ; ΔS°= -219.9 J/K -72.9 kJ -188 kJ +243 kJ -92.5 kJ +84.9 kJ

-72.9 kJ

Below what temperature does the following reaction become nonspontaneous? 2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) ΔH = +136.5 kJ; ΔS = +287.5 J/K 39.2 K 475 K 151 K This reaction is nonspontaneous at all temperatures. This reaction is spontaneous at all temperatures.

475 K

Above what temperature does the following reaction become nonspontaneous? 2 H2S(g) + 3 O2(g) → 2 SO2(g) + 2 H2O(g) ΔH = -1036 kJ; ΔS = -153.2 J/K 298 K 158.7 K 6.762 × 103 K This reaction is nonspontaneous at all temperatures. This reaction is spontaneous at all temperatures.

6.762 × 103 K

Which of the following processes have a ΔS < 0? carbon dioxide(g) → carbon dioxide(s) isopropyl alcohol condenses water freezes methanol (g, at 555 K) → methanol (g, at 400 K) All of the above processes have a ΔS < 0.

All of the above processes have a ΔS < 0.

Which of the following processes have a ΔS > 0? 1)Na2CO3(s) + H2O(g) + CO2(g) → 2 2)NaHCO3(s) 3)CH4(g) + H2O(g) → CO(g) + 3 H2(g) 4)N2(g) + 3 H2(g) → 2 NH3(g) CH3OH(l) → CH3OH(s) 5)All of the above processes have a ΔS > 0.

CH4(g) + H2O(g) → CO(g) + 3 H2(g)

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part H In addition, predict under what temperatures (all temperatures, low temperatures, or high temperatures), if any, the reaction in part D is spontaneous. The reaction is spontaneous at all temperatures. The reaction is spontaneous at low temperatures. The reaction is spontaneous at high temperatures. The reaction is nonspontaneous at all temperatures.

The reaction is nonspontaneous at all temperatures.

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part F In addition, predict under what temperatures (all temperatures, low temperatures, or high temperatures), if any, the reaction in part B is spontaneous. The reaction is spontaneous at all temperatures. The reaction is spontaneous at low temperatures. The reaction is spontaneous at high temperatures. The reaction is nonspontaneous at all temperatures.

The reaction is spontaneous at high temperatures.

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part E In addition, predict under what temperatures (all temperatures, low temperatures, or high temperatures), if any, the reaction in part A is spontaneous. The reaction is spontaneous at all temperatures. The reaction is spontaneous at low temperatures. The reaction is spontaneous at high temperatures. The reaction is nonspontaneous at all temperatures.

The reaction is spontaneous at low temperatures.

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part G In addition, predict under what temperatures (all temperatures, low temperatures, or high temperatures), if any, the reaction in part C is spontaneous. The reaction is spontaneous at all temperatures. The reaction is spontaneous at low temperatures. The reaction is spontaneous at high temperatures. The reaction is nonspontaneous at all temperatures.

The reaction is spontaneous at low temperatures.

Consider a reaction that has a positive ΔH and a negative ΔS. Which of the following statements is TRUE? This reaction will be nonspontaneous only at high temperatures. This reaction will be spontaneous only at high temperatures. This reaction will be nonspontaneous at all temperatures. This reaction will be spontaneous at all temperatures. It is not possible to determine without more information.

This reaction will be nonspontaneous at all temperatures.

Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is TRUE? This reaction will be spontaneous only at high temperatures. This reaction will be nonspontaneous at all temperatures. This reaction will be nonspontaneous only at high temperatures. This reaction will be spontaneous at all temperatures. It is not possible to determine without more information.

This reaction will be nonspontaneous only at high temperatures

Identify the change in state where ΔS decreases. liquid to gas solid to liquid gas to solid solid to gas

gas to solid

Calculate the change in Gibbs free energy for each of the following sets of ΔHrxn, ΔSrxn, and T. Part A ΔH∘rxn=+ 81 kJ , ΔSrxn=+ 143 J/K , T= 301 K Express your answer as an integer. ΔG =?

ΔG = 38 kJ

Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 298 K. Predict whether or not this reaction will be spontaneous at this temperature. N2(g) + 2 O2(g) → 2 NO2(g) ΔH = +66.4 kJ ΔSsurr = +223 J/K, reaction is spontaneous ΔSsurr = +66.4 kJ/K, reaction is not spontaneous ΔSsurr = -66.4 J/K, reaction is spontaneous ΔSsurr = -223 J/K, reaction is not spontaneous ΔSsurr = -66.4 J/K, it is not possible to predict the spontaneity of this reaction without more information.

ΔSsurr = -223 J/K, reaction is not spontaneous

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part D CO2(g)→C(s)+O2(g)ΔH∘rxn=+393.5kJ ΔSsys>0, ΔSsurr>0 ΔSsys<0, ΔSsurr>0 ΔSsys>0, ΔSsurr<0 ΔSsys<0, ΔSsurr<0

ΔSsys<0, ΔSsurr<0

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part A 2CO(g)+O2(g)→2CO2(g)ΔH∘rxn=−566.0kJ ΔSsys>0, ΔSsurr>0 ΔSsys<0, ΔSsurr>0 ΔSsys>0, ΔSsurr<0 ΔSsys<0, ΔSsurr<0

ΔSsys<0, ΔSsurr>0

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part C 2H2(g)+O2(g)→2H2O(g)ΔH∘rxn=−483.6kJ ΔSsys>0, ΔSsurr>0 ΔSsys<0, ΔSsurr>0 ΔSsys>0, ΔSsurr<0 ΔSsys<0, ΔSsurr<0

ΔSsys<0, ΔSsurr>0

Without doing any calculations, determine the sign of ΔSsys and ΔSsurr for each chemical reaction. Part B 2NO2(g)→2NO(g)+O2(g)ΔH∘rxn=+113.1kJ ΔSsys>0, ΔSsurr>0 ΔSsys<0, ΔSsurr>0 ΔSsys>0, ΔSsurr<0 ΔSsys<0, ΔSsurr<0

ΔSsys>0, ΔSsurr<0