Student Number for Alphabetizing: Last )ven ?krnR4dn Name First Chem: 126 Sectio

Question

Student Number for Alphabetizing: Last )ven ?krnR4dn Name First Chem: 126 Section Thermodynamics part 1 March 26th 1. (2 points) CH) +3 Cle) CHCh+3HC Compound CH4(g) | CHCI3(1) | HCl(E) AG-50.5-73.3 95.3 (a) Calculate the change in the standard Gibbs free energy AG of the reaction at room temperature (b) Is the reaction spontaneous under standard conditions? (e) Without caleulations: Is the change in the standard entropy of the reaction AS° positive or n (d) From the signs of ?Go and AS" decide whether the reaction is endothermic or exothermic. (e) Will the reaction become more spontaneous or less spontaneous if the temperature is raise For a rractin with AH- -50k and AS150, find at what temperatu

Explanation / Answer

a) Change in standard Gibbs free energy ?Go of the reaction at room temperature can be calculated by the formula:

?G0 = ??G0(products) ? ??G0(reactants)

Only gaseous species present in the reaction equation are used in the above formula

So,   ?G0f (CH4) = -50.5 kJ/mol

  ?G0f (CHCl3) = -73.3 kJ/mol

?G0f (HCl) = -95.3 kJ/mol

So,  ?G0 = ( 3x (-95.3) + (-73.3)) - (-50.5)

Note: Stoichiometry of reactants and products plays a very important role in the above equation as ?G0f will be multiplied with the stoichiometry of that particular species.

= -359.2 + 50.5

= -308.7 kJ/mol

So, Change in standard Gibbs free energy ?Go =  -308.7 kJ/mol .

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