Enthalpy, Entropy, and Free Energy

2N2(g) + O2(g)→ 2N2O(g) ΔSrxn =

-148 J/K

3H2(g) + N2(g) → 2NH3(g) ΔSrxn =

-198 J/K

Use this information to calculate ΔGrxn. ΔGrxn = ____kJ

-2453.1

Consider the following data: equestion Using these data, calculate ΔHrxn for this chemical reaction. Round to the nearest whole number. 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g) ΔHrxn=

-2856 kJ

Use this information to calculate ΔGrxn at 298 K. ΔGrxn=____kJ

-33.3

CH4(g) + 2O2(g) →CO2(g) + 2H2O(g) ΔSrxn =

-5 j/k

Consider the following data: S(s) + O2(g) → SO2(g) ΔHrxn = -297 kJ 2SO3(g) → 2SO2(g) + O2(g) ΔHrxn = 198 kJ Use Hess's law to determine ΔHrxn for this reaction: 2S(s) + 3O2(g) → 2SO3(g) ΔHrxn = kJ

-792 kj

The Second Law of Thermodynamics states that the overall entropy of the universe (or any other isolated system) can never decrease. Identify the systems to which the Second Law of Thermodynamics would apply.

....

Identify each of these reactions as being spontaneous or nonspontaneous.

.....

Use the information in the table to calculate Δ Srxn for each of these reactions. Round all answers to nearest whole number.

.....

Choose the system from each pair that likely has the higher entropy.

1 mol NaBr dissolved in 1 L water

1 mol NaBr dissolved in 1 L water

3 mol N2 gas and 2 mol O2 gas mixed together

CH3COOH(aq) + NaHCO3(s) g →CO2(g) + H2O(l) + Na+(aq) + CH3COO-(aq) ΔHrxn > 0

endothemic

NH4Cl(s) → NH4+(aq) + Cl-(aq) ΔHrxn = 14.7 kJ

endothermic

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) ΔHrxn < 0

exothermic

NaOH(s) NaOH(s) → Na+(aq) + OH-(aq) ΔHrxn = -44.5 kJ

exothermic

Choose the system from each pair that likely has the higher entropy.

ice water

Choose the system from each pair that likely has the higher entropy.

liquid water at 90°C

These reactions are all spontaneous. Based on this information, is enthalpy of reaction a reliable indicator of whether a reaction is spontaneous?

no

3

nonspontaneous

a reaction vessel that is completely sealed and insulated

second law applies

a sealed glass flask that is not insulated

second law does not apply

an open beaker containing an aqueous solution

second law does not apply

the Earth

second law does not apply

1

spontaneous

2

spontaneous

For each of these equations, predict the effects of temperature on the spontaneity of the reaction. 2N2O(g) es001-1.jpg 2N2(g) + O2(g) es001-2.jpgH < 0; es001-3.jpgS > 0 H2O(l) es002-1.jpg H2O(g) es002-2.jpgH > 0; es002-3.jpgS > 0 3O2(g) es003-1.jpg 2O3(g) es003-2.jpgH > 0; es003-3.jpgS < 0 C(s) + 2Cl2(g) es004-1.jpg CCl4(g) es004-2.jpgH < 0; es004-3.jpgS < 0

spontaneous at all temp only at high temp nonspntanous all temp spontaneous only at low