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Chemical thermodynamics in the manufacture of methanol Methanol (CH3OH) is used to manufacture a large number of important chemicals, such as formaldehyde (HCHO) which is employed in the manufacture of a variety of polymers; methyl-tertiary-butylether((CH3)3OCH3), which has been used as a lead-free anti-knocking agent in petrol; acetic acid (CH3CO₂H), etc. Annual production of methanol has been increasing: from 3.3 MTe/yr in 1982,¹ to 20 M Te/yr in 1991.² Methanol is manufactured using synthesis gas (a mixture of carbon monoxide,CO, and hydrogen, H₂) through the following chemical equilibrium. \mathrm{CO}(g)+2 \mathrm{H}_{2}(g) \rightleftarrows \mathrm{CH}_{3} \mathrm{OH}(\mathrm{g}) Thermodynamic data (standard enthalpies of formation, AH₁º, absolute entropies, Sº, and heat capacities (Cp) at 298 K) corresponding to the five chemical species in the above chemical reactions are given in Table 1 below.³

(a) Use the data in Table 1 to calculate the following.

(i) The enthalpy change for the reaction, under standard conditions. Comment on your answer. (ii)The standard entropy change for the reaction. Comment on your answer. (iii)The standard Gibbs energy change for the reaction, under standard conditions. Comment on your answer. (iv)The equilibrium constant for the reaction equilibrium, under standard conditions. Comment on your answer. (v)The change in the heat capacity at constant pressure for the chemical reactions, under standard conditions.

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