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Tutorial 5 Answer Presentation

Tutorial 5 Answer Presentation. Hu Peiyu 12S7F. Question 2. a) H ess’s law states that the enthalpy change ( Δ H) of a particular reaction is determined only by the initial and final state of the system regardless of the pathway taken. Question 2. b) i) K 2 CO 3 +2HCl→ 2KCl+H 2 O+CO 2

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Tutorial 5 Answer Presentation

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  1. Tutorial 5 Answer Presentation Hu Peiyu 12S7F

  2. Question 2 • a) Hess’s law states that the enthalpy change (ΔH) of a particular reaction is determined only by the initial and final state of the system regardless of the pathway taken.

  3. Question 2 • b) i) K2CO3+2HCl→2KCl+H2O+CO2 • ii) Heat evoved: q=m∙c∙ΔH=V/ρ∙c∙ΔT =30.0/1.0*4.2*5.2 =655J ΔHr=-q/n=625J/0.020mol=-32.8KJ/mol

  4. Question 2 • iii) because HCl is in excess in this reaction, the concentration of it need not to be exact.

  5. Question 2 • c) i) KHCO3+HCl→KCl+H2O+CO2 • ii) Heat absorbed: q=m∙c∙ΔH=m∙c∙ΔT =30.0*4.2*3.7 =466.2 ΔH=466.2/0.020=23.3KJ/mol

  6. Question 2 • d) Energy/ kJmol-1 K2CO3+2HCl ΔH=-32.8kJ Hd=? KCl+H2O+CO2 ΔH=23.3kJ KHCO3+HCl

  7. Question 2 • By Hess’s law • Hd(KHCO3)=23.3kJ-(-32.8kJ)=56.1kJ

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