JEOPARDY ANSWERS: ENTHALPY: 100: ΔH A. Ice melting is the correct answer. Ice must take in energy to melt, so it is endothermic. 200: 92 J. Use q = mcΔT to solve this problem. m = mass, c = specific heat, = change in temp. 300: ΔT 63 kJ are released 400: 571.6 kJ 500: ENTROPY: 100: Spontaneous means something occurs without outside intervention (in other words, a reaction or process that happens on its own). Any reaction/process that requires adding heat, electricity, or energy in ANY form is NOT spontaneous. 200: C. The entropy of the universe must be positive in order for a reaction to be spontaneous. 300: A is the correct answer. Justification: Reactions are spontaneous when is negative. Using the equation = ΔG ΔG ΔH – TΔS, we can predict the sign of if we know values for and (See table below) ΔG ΔH ΔS. ΔH ΔS ΔG Depends on temperature (high temps are + + spontaneous, low temps are not) Depends on temperature (low temps are – – spontaneous, high temps are not) + – – + + – 400: C (see justification above) 500: C = products reactants, so = ΔH – ΔH (-763.2) (-804.2) = 41 kJ/mol ΣHf ΣHf –
JEOPARDY ANSWERS: ENTHALPY: 100: ΔH 200: A. Ice melting is the correct answer. Ice must take in energy to melt, so it is endothermic. 300: 92 J. Use q = mcΔT to solve this problem. m = mass, c = specific heat, ΔT = change in temp. 400: 63 kJ are released 500: 571.6 kJ ENTROPY: 100: Spontaneous means something occurs without outside intervention (in other words, a reaction or process that happens on its own). Any reaction/process that requires adding heat, electricity, or energy in ANY form is NOT spontaneous. 200: C. The entropy of the universe must be positive in order for a reaction to be spontaneous. 300: A is the correct answer. Justification: Reactions are spontaneous when ΔG is negative. Using the equation ΔG = ΔH – TΔS, we can predict the sign of ΔG if we know values for ΔH and ΔS. (See table below) ΔH ΔS ΔG + + Depends on temperature (high temps are spontaneous, low temps are not) – – Depends on temperature (low temps are spontaneous, high temps are not) – + – + – + 400: C (see justification above) 500: C ΔH = ΣHf products – ΣHf reactants, so ΔH = (-763.2) – (-804.2) = 41 kJ/mol