Chemistry

Problem

To manufacture acrylamide industrially, engineers consider a two-step process: 1. Hydrolyze nitrile groups of acrylonitrile using water to form acrylamide. This hydrolysis is slow and has

\Delta G^{\circ}=+15\,\text{kJ mol}^{-1}

. 2. Couple the step above to one or more highly exergonic reactions carried out in the same reactor. Plant safety regulations impose two constraints on the choice of driving reaction(s): • No reaction may involve elemental hydrogen or oxygen (to avoid explosion hazards). • Total energy release per mole of acrylamide produced must not exceed

40\,\text{kJ}

in magnitude (to limit cooling requirements). Table 4 lists three candidate reactions available at scale. Table 4 Industrial Driving Reactions (all liquid phase)

Label	Reaction	$\Delta G^{\circ}\,(\text{kJ mol}^{-1})$
X	hydrolysis of phosphoric anhydride linkage in polyphosphate waste	−31
Y	isomerization of glucose-6-phosphate to fructose-6-phosphate	−1.7
Z	neutralization of sulfuric acid with aqueous ammonia	−46

(a) For each single reaction X, Y, or Z, determine whether coupling it alone to the acrylonitrile hydrolysis step satisfies both safety constraints while rendering the overall process favorable. Show numerical support. (b) Propose one combination of two driving reactions from Table 4 that, when operated at a

1{:}1

stoichiometric ratio with the hydrolysis step, meets both safety constraints. Write the resulting overall reaction and compute its

\Delta G^{\circ}_{\text{overall}}

. (c) The plant management favors minimal energy waste. Justify why your choice in part (b) meets this goal better than using reaction Z alone, even though reaction Z by itself can render the hydrolysis favorable. (a) Evaluation of single-reaction coupling (b) Design of dual-reaction coupling and

\Delta G^{\circ}

calculation (c) Energy-waste justification

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