Question 1 (c)

Of C2H5NH2(aq) and C2H5NH3+(aq) , which is present in the solution at the higher concentration at equilibrium? Justify your answer. C2H5NH2 is present in the solution at the higher concentration at equilibrium. Ethylamine is a weak base and thus it has a small K value. Therefore only partial dissociation of C2H5NH2 occurs in water, and \[C2H5NH3+\] is thus less than \[C2H5NH2\]. One point is earned for the correct answer with justification.

Question 5 (c)

Given that M-12098 for the reaction is —92.2 kJ mol-I, which is larger, the total bond dissociation energy of the reactants or the total bond dissociation energy of the products? Explain. AH%8 E (bond energy of the reactants) — E (bond energy of the products) Based on the equation above, for Al-12098 to be negative, the total bond energy of the products must be larger than the total bond energy of the reactants. OR More energy is released as product bonds are formed than is absorbed as reactant bonds are broken. One point is earned for the correct answer with the correct equation and explanation.

ENERGY bonds broken endothennic reactants bonds Inade exothennic roducts overall heat taken m (absorbed) ENDOTHERMC course of reaction (c) doc b

ENERGY bonds broken endothermic reactants EXOTHERMC (c) doc b bonds Inade exothermic overall heat given out to surroundings products course of reaction

If we consider the reaction between hydrogen (1-12) and oxygen (02) to form water (H20), we see that the products have less energy than the reactants: 2/-12 + 02 13671<J/mo/ 2/-120 18521<J/mo/ We know this because we can look up the bond energies of the different bonds that are breaking and forming, and add them up to find the total energy of both sides of the reaction: = 436 kJ/mol x2 molecules of 1-12 872 kJ/mol total energy H-o = 463 kJ/m01 = 495 kJ/m01 xl molecules of 02 495 kJ/mol total energy 1367 kJ/m01 x2 bonds per molecule of H20 926 kJ/mol energy per molecule formed X 2 molecules formed in the reaction 1852 kJ/m01 Because the formation of the products releases more energy (1852 kJ/mol) than the energy required to break the bonds of the reactants (1367 kJ/mol), this reaction is exothermic.

Question 5 (e)

(i) Explain why there is a temperature above 298 K at which the algebraic sign of the value of AGO changes. AGO AHO - TASO As the temperature increases ITASOI will at some point exceed IN-PI. Because both AHO and ASO are negative, the sign of AGO will then change from negative to positive. One point is earned for the correct explanation.

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