Running head: HEAT OF NEUTRALIZATION 1 Heat of Neutralization Lee Choy Yee B1602062 HELP University
HEAT OF NEUTRALIZATION 2 Heat of Neutralization Objectives 1. To determine the enthalpy of dissolution of solid NaOH. 2. To determine the enthalpy of solution between solid NaOH and HCl. 3. To determine the enthalpy of neutralization between NaOH and HCl. 4. To study Hess’s Law by determining the heat of reaction using Styrofoam cups as calorimeter. Introduction The enthalpy of neutralization (ΔHn) is the change in enthalpy that occurs when one equivalent of an acid and one equivalent of a base undergo a neutralization reaction to form water and a salt (Chang & Goldsby, 2016). It is also defined as the energy released with the formation of 1 mole of water (Chang & Goldsby, 2016). A calorimeter can be used to measure the quantity of heat released or absorbed during the reaction from the changes of temperature of water. The specific heat capacity of water is 4.184 J/g o C, which means 4.184 J of energy is needed to increase 1 gram of water by 1 o C (Chang & Goldsby, 2016). In this experiment, a calorimeter was set up to monitor the heat changes of three different reactions. First, solid NaOH is added into water in calorimetry. Subsequently, the reaction is repeated by dissolving solid NaOH in HCl solutions. Then, experiment is also repeated using NaOH solutions and HCl solutions. The hypothesis of this experiment is: 1. The enthalpy of dissolution of NaOH is -44.51 kJ/mol (Haynes, 2010). 2. The enthalpy of neutralization of HCl and NaOH is 58 kJ/mol (Haynes, 2010). 3. The enthalpy of solution between solid NaOH and HCl solutions is equal to the sum of enthalpy of dissociation of NaOH and neutralisation of NaOH and HCl solutions. 4. The enthalpy of reaction could be determined by using Hess’s law and calorimetry. Materials 1. Styrofoam cups 2. Slit plastic container as lid 3. Thermometer 4. Glass rod 5. Electronic balance 6. Weighing Bottle 7. 100 mL measuring cylinder 8. 100 mL beaker 9. Solid NaOH 10. 0.5 M NaOH 11. 0.25 M HCl 12. 0.5 M HCl Method 1. A calorimeter was set up using two nested Styrofoam cups with thermometer as shown in Figure 1
HEAT OF NEUTRALIZATION 3 Figure 1. Apparatus set up to modify calorimetry and measure the temperature changes of each reaction. 2. A mass of 1.01 g of solid NaOH was weighed and added into calorimeter along with 81 mL tap water. 3. The container was rinsed between each set of reactions. 4. All observation and data were recorded. 5. Step1 to 4 was repeated twice by reacting 1.03 g of solid NaOH with 81 mL of 0.25 M HCl and 39 mL of 0.5 M NaOH solutions and 39mL of 0.5 M HCl solutions. Results All observation and data collected is recorded in Table 1, 2 and 3 respectively. Table 1 Observation for Each Reaction to Determine the heat of reaction per mole of NaOH used in the reaction Reaction Observation 1 Temperature increases rapidly and maintained at 28 o C after solid NaOH is added.
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