3_energetic

# 3_energetic - < energetic/AL90P1_2b 2(b Show how H o for...

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<<< energetic/AL90P1_2b 2. (b) Show how o f H for CuSO 4 .5H 2 O(s) can be determined using the following data: o so H ln CuSO 4 .5H 2 O(s) = +8 kJ mol -1 o so H ln CuSO 4 (s) = -66 kJ mol -1 o f H CuSO 4 (s) = -773 kJ mol -1 o f H H 2 O(l) = -286 kJ mol -1 (3 marks) <<< energetic/AL90P2_4c 4. (c) Account for the following observations. Dinitrogen tetraoxide and hydrogen peroxide are both unstable to heat. (3 marks) <<< energetic/AL91P1_4b 4. (b) You are required to determine indirectly the enthalpy of formation of calcium carbonate(s). You are given the reagents: calcium, calcium carbonate, a strong acid, and water; the enthalpies of formation of carbon dioxide(g) and water(l) are available. (i) Give equations of suitable reactions for this determination. [Work out the energy cycle of the determination] (ii) Name the major pieces of apparatus needed for this determination. (iii) Suggest one experimental difficulty in the direct determination of the enthalpy of formation of calcium carbonate from its element. (6 marks) <<< energetic/AL91P2_1b 1. (b) (i) Calculate the enthalpy of formation of NaCl(s) from the following Reaction o H / kJ mol -1 NaOH(aq) + HCl(aq) -----> NaCl(aq) + H2O(l) -57.3 ) ( ) ( 2 1 ) ( 2 2 2 l O H g O g H + -285.9 ) ( ) ( 2 2 1 ) ( 2 1 2 g HCl g Cl g H + -92.3 ) ( ) ( aq HCl aq g HCl + -71.9 ) ( ) ( 2 1 ) ( 2 1 ) ( 2 2 aq NaOH aq g O g H s Na + + + -425.6 NaCl(s) + aq NaCl(aq) +3.9 (ii) The enthalpy of neutralization of ethanoic acid with aqueous sodium hydroxide is -55.2 kJ mol -1 while that of hydrochloric acid is -57.3 kJ mol -1 . Account for the difference in these two values. (iii) When solid sodium chloride is dissolved in water, the process is endothermic. Explain this observation. (8 marks) <<< energetic/AL92P2_1b 1. (b) (i) Define the standard enthalpy of formation of a compound, using CH 3 OH(l) as an illustration. (ii) Given the following thermochemical data at 298 K:

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Standard enthalpy of combustion of CH 3 OH(l) -726.6 kJ mol -1 Standard enthalpy of formation of CO 2 (g) -393.5 kJ mol -1 Standard enthalpy of formation of H 2 O(l) -285.8 kJ mol -1 Calculate the standard enthalpy of formation of CH 3 OH(l) at 298 K. (4 marks)
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3_energetic - < energetic/AL90P1_2b 2(b Show how H o for...

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