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3 marksEnergetics

CSEC Chemistry · May/June 2005 · Paper 2 · Question 4(c)(iii)

When 12.0 g potassium nitrate (KNO₃) is dissolved in 100 cm³ of water, the temperature drops by 4.20 °C. Given: Relative atomic mass: K=39, N=14; O=16. Specific heat capacity of water = 4.2 J g⁻¹ K⁻¹. Heat change = M x C x ΔT. 1 cm³ of solution = 1 g. Using the above information calculate EACH of the following: The number of moles of KNO₃ used in the experiment.

Draw a labelled energy profile diagram to represent the enthalpy change for the reaction.

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Other parts of this question

  1. 4(a)What changes occur during a reaction that can account for this fact?[3 marks]
  2. 4(b)(i)Define the term 'heat of neutralization'.[1 mark]
  3. 4(b)(ii)It is observed that whenever a strong acid (such as HCl or HNO₃) is completely neutralized by a strong base (such as NaOH or KOH), the heat of neutralization…[2 marks]
  4. 4(c)(i)a)The number of moles of KNO₃ used in the experiment.[1 mark]
  5. 4(c)(i)b)The heat change for the reaction.[1 mark]
  6. 4(c)(i)c)The enthalpy change in kJ mol⁻¹ for the reaction.[2 marks]
  7. 4(c)(ii)State ONE assumption you made in your calculation.[1 mark]

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