Question

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AH and Calorimetry: Suppose 33mL of 1.20M HCl is added to 42mL of a solution containing excess sodium hydroxide in a coffee-cup calorimeter. The solution temperature, originally at 25.0°C, rises to 31.8°C. COMPARE ANSWER WITH PROBLEM #9. 2pts a Provide a thermochemical equation, including AH in kJ. (include sign) b. What is the energy (AH) evolved in kJ per mole of HCI? (include sign) For simplicity, assume the heat capacity and the density of the final solution are those of H2O. (Note: in more accurate work, these values are not the same and must be calculated). Also assume that the total volume of the solution equals the sum of the volumes of HCl(aq) and NaOH(aq). work space Provide a thermochemical equation. Must include sign b)

Answer 1

(a)

Thermochemical equation :

HCl(aq) + NaOH(aq) $\rightarrow$ NaCl(aq) + H₂O(l) ∆H= -2.134kJ

Heat released by neutralization of acid = m.s.∆T

= (33+42)ml×1g/ml × 4.184J/g.℃ × (31.8-25.0)℃ = 2133.84 J

= 2.13384kJ = 2.134kJ

∆H = -2.134kJ (Answer)

(b)

Heat released due to neutralization of 33ml , 1.20M HCl

Number of moles of HCl = 1.20mol/L × 33×10^-3L

= 3.96×10^-2mol

∆H = - 2.13384kJ/(3.96×10^-2mol)

= -53.8848kJ/mol

= - 53.88 kJ/mol. (Answer)