• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9

Enthalpy change of neutralisation.

Extracts from this document...

Introduction

Topic: Enthalpy change of neutralisation. I familiarised myself with the Material Safety Data Sheets of toxic substances. PLANNING (A) Enthalpy (H)1 - The sum of the internal energy of the system plus the product of the pressure of the gas in the system and its volume: Esys is the amount of internal energy, while P and V are respectively pressure and volume of the system. To measure the enthalpy we have to first figure out the mass of a substance under a constant pressure and determine the internal energy of the system. The enthalpy change (H)2 is the amount of heat released or absorbed when a chemical reaction occurs at constant pressure. The standard enthalpy change of neutralization3 is the change in enthalpy that occurs when an acid and base undergo a neutralization reaction to form one mole of water under standard conditions (298k and 1atm), i.e. react to produce water and a salt. It is a special case of the standard enthalpy change of reaction. HCl (aq) + NaOH (aq) � NaCl (aq) + H2O (l) H+ + Cl- + Na+ + OH- � Na+ + Cl- + H2O H+ + OH-� H2O Heat energy = ms?T. The amount of reat required will depend on how much of the substance there is to heat, what is it made of and the amount by which the temperature is increased. ...read more.

Middle

e) HCl (aq) + NaOH (aq) � NaCl (aq) + H2O (l) Amount of hydrochloric acid 30 cm3 Temperature of hydrochloric acid 20.5 oC Amount of 4 mol dm-3 sodium hydroxide 30 cm3 Temperature of 4 mol dm-3 sodium hydroxide 22.5 oC Amount of the mixture 60 cm3 Temperature of the mixture 33.0 oC Table 5. DATA PROCESSING AND PRESENTATION Heat required = ms?T m =d V n = c V ?T = Tmix - (T1 + T2) ?H = heat required * 1/n s = 4.18 J g-1 K-1 The amount of heat required to heat the water can be calculated as follows (we assume that the heat energy required to change the temperature of the other substances present may be ignored): a) HCl (aq) + NaOH (aq) � NaCl (aq) + H2O (l) V = 60 cm3 d = 1.00 g cm-3 m = d V = 60 cm3 * 1.00 g cm-3 = 60 g ?T = Tmix - 1/2(T1 + T2) = 31.0 oC - 20.0 oC = 11.0 oC heat required = ms?T = 60.0 g * 4.18 J g-1 K-1 * 11.0 oC = 2758 J = 2.758 kJ nHCl = c V = 2 mol dm-3 * 0.3 dm-3 = 0.06 moles nNaOH = c V = 2 mol dm-3 * 0.3 dm-3 = 0.06 moles ?H = heat required * 1/n = 2.758 kJ * 1/0.06 moles = 45.97 kJ mol-1 ?H = - 45.97 kJ mol-1 b) ...read more.

Conclusion

kJ * 1/0.06 moles = 48.07 kJ mol-1 ?H = - 48.07 kJ mol-1 CONCLUSION AND EVALUATION As we can see from the results above, the prediction made at the very beginning of this lab was correct. Neither type of acid or base nor the concentration of acid does not have influence on the enthalpy of neutralisation. Hence we may assume that the enthalpy of neutralisation is equal to the enthalpy change for H+ + OH-� H2O. The enthalpy change for this reaction, however, is -57.9 kJ mol-1. The differences between my results and the theoretical value may come from the fact that the measurements were not very accurate. The temperatures of the acids, bases and mixtures might have been influenced by cool beakers. Therefore the temperatures were a bit lower than they should have been. If the ?T was higher by 3oC, the enthalpy of neutralisation would be almost the same as in the sources. I do not know how to improve the experiment so that data gathered will be similar to theoretical values. I reckon in classroom conditions such mistake is not a serious one. SOURCES: 1. Green J, Damji S. 2001. Chemistry. Second edition. IBID Press, Victioria, Australia. 2. http://en.wikipedia.org/wiki/Standard_enthalpy_change_of_neutralisation 1 The definition comes from http://www.chem.tamu.edu/class/majors/tutorialnotefiles/enthalpy.htm 2 The definition comes from http://www.ausetute.com.au/enthchan.html 3 The definition comes from http://en.wikipedia.org/wiki/Standard_enthalpy_change_of_neutralisation ENTHALPY CHANGE OF NEUTRALISATION 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. Marked by a teacher

    Investigating The Energy Change During A Neutralisation Reaction.

    4 star(s)

    Bond making is exothermic and energy is released into its surroundings. Endothermic reactions absorb energy; the energy continues to be absorbed as long as the reaction continues. Bond breaking is endothermic and energy is absorbed from its surroundings. Every reaction can be considered as a series of bond breaking steps followed by bond forming steps.

  2. Marked by a teacher

    Enthalpy of Neutralisation.

    3 star(s)

    compared to the strong acids, which dissociate in water. Also, the pH level (acidity) of ethanoic acid is lower than hydrochloric acid and sulphuric acid. While hydrochloric acid and sulphuric acid have a pH of 1, which is acidic, (the solution contains free roaming H+ ions. It usually contains hydrogen ions that dissolve in water to produce hydrogen ions

  1. To investigate the effect of concentration on the temperature rise, heat evolved and heat ...

    Volume (cm3) Exp 1 - Final Temperature (�C) Exp 2 - Final Temperature (�C) Average Temperature (�C) 0.00 26.00 26.00 26.00 5.00 31.00 31.20 31.10 10.00 35.00 35.00 35.00 15.00 38.10 38.90 38.50 20.00 42.40 42.60 42.50 25.00 44.00 44.00 44.00 30.00 43.50 43.50 43.50 35.00 41.30 41.70 41.50 40.00

  2. How much Iron (II) in 100 grams of Spinach Oleracea?

    Wash the beaker and glass rod twice using a small volume of Sulphuric Acid (aq) to collect up any remaining Iron (II). 8) Wash the residue in the funnel once with a little Sulphuric Acid (aq) and collect the filtrate.

  1. Investigate a neutralisation reaction between hydrochloric acid and sodium hydroxide.

    The factor I will choose to vary is the concentration of the hydrochloric acid. To keep this a fair test I will have to keep the other the factors constant. The temperature will remain constant by using the room temperature (25?c). The concentration of the sodium hydroxide will be constant.

  2. Analysing; Enthalpy of Decomposition of Sodium Hydrogencarbonate

    x -7.0 = - 984.9 J Internal energy change = 984.9 J Enthalpy change of neutralisation = Internal energy change No. Of moles of solid used = 984.9/0.042 = 23450 J/mol = 23.5 kJ/mol Experiment 2 (T = T2 - T1 = 12.1- 20.0 = -7.9 0C Energy transferred to

  1. Investigating Neutralisation.

    + Na+ OH- (aq) Na+ Cl- + H2O Erase spectator ions H+ (aq) + OH- (aq) H2O (l) Exothermic reaction This is the ionic equation for the neutralisation of any acid and alkali. When the solutions of acid and alkali are mixed, hydrogen ions, H+ (aq), and hydroxide ions, OH- (aq)

  2. Explain how the enthalpy change of neutralisation can be used to determine the relative ...

    The ions react very easily to reform the acid and the water. At any one time, only about 1% of the ethanoic acid molecules have converted into ions. The rest remain as simple ethanoic acid molecules. Most organic acids are weak. Hydrogen fluoride (dissolving in water to produce hydrofluoric acid)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work