experiment report 1.3.docx - CHEMISTRY EXPERIMENT REPORT...

CHEMISTRY EXPERIMENT REPORT
Determination of Enthalpy Change Based on
the Principles of Calorimetry
Santa Laurensia
Senior High School
Year 2019-2020
Made By:
Angelica Grace XIA1/01

1. Objective :
To investigate the Energy Change in Neutralization Reaction and Dissolution of Urea
2. Background Theory
The standard enthalpy change of neutralization is the enthalpy change when solutions
of an acid and an alkali react together under standard conditions to produce 1 mole of water.
Notice that enthalpy change of neutralization is always measured per mole of water formed.
Enthalpy changes of neutralization are always negative - heat is released when an acid and
and alkali react. For reactions involving strong acids and alkalis, the values are always very
closely similar, with values between -57 and -58 kJ mol -1 . That varies slightly depending on the
acid-alkali combination (and also on what source you look it up in!).
Why do strong acids reacting with strong alkalis give closely similar values?
We make the assumption that strong acids and strong alkalis are fully ionized in
solution, and that the ions behave independently of each other. For example, dilute
hydrochloric acid contains hydrogen ions and chloride ions in solution. Sodium hydroxide
solution consists of sodium ions and hydroxide ions in solution. The equation for any strong
acid being neutralized by a strong alkali is essentially just a reaction between hydrogen ions
and hydroxide ions to make water. The other ions present (sodium and chloride, for example)
are just spectator ions, taking no part in the reaction.
The full equation for the reaction between hydrochloric acid and sodium hydroxide solution is:
NaOH(aq)+HCl(aq)→NaCl(aq)+H2O(l)(1)(1)NaOH(aq)+HCl(aq)→NaCl(aq)+H2O(l)
but what is actually happening is:
OH−(aq)+H+(aq)→H2O(l)(2)(2)OH−(aq)+H+(aq)→H2O(l)