Use the data given below to answer the next three questions. For the reaction: S

Question

Use the data given below to answer the next three questions. For the reaction: Si(s) + 2 F2(g) SiF4 (g) AHo (k/mol) 0 0 1614.9 G",(kj/mol) 0 0-15727 So(J/mol K) 18.83 202.8 282.4 Calculate the enthalpy of the reaction under standard conditions. Report your answer to one decimal place, in k (do not include the units in the text box). Make sure to indicate negative sign where appropriate. For example, enter -1234.5 for -1234.5 k] kj Calculate the entropy of the reaction under standard conditions. Report your answer to one decimal place, in J/K (do not include the units in the text box). Make sure to indicate negative sign where appropriate. For example, enter -123.0 for -123.0 J/K /K The temperature range for which the above reaction is spontaneous is T11370 K O T

Explanation / Answer

Si(s) + 2 F2 (g) ------> SiF4 (g)

Enthapy of reaction dH rxn can be calculated as follows

dH rxn = dH products - dH reactants

dH rxn = dH SiF4 - (dH si + 2 * dH F2)

dH rxn = (-1614.9) -(0 + 0)

dH rxn = -1614.9 kJ/mol

Entropy of the reaction dS rxn can be calculated as follows

dS rxn = dS products - dH reactants

dS rxn = dS SiF4 - (dS Si + 4(dS F2))

dS rxn = 282.4 - (18.83 +2(202.8))

dS rxn = -142.03 J/mol K

For spontaneous reaction

T > dH/dS

T > -1614.9 * 10^3/(-142.03)

T > 11370 K the the reaction will become spontaneous

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