Introduction
The purpose of this experiment was to heat the dissolution of NaOH, determining heat capacity of the calorimeter and neutralization of a strong base with a strong acid. A heat of reaction, qrxn is the quantity of heat exchanged between a system and its surroundings when a chemical reaction occurs within the system at constant temperature (Petrucci et al., 2011). A calorimeter is a device measuring quantities of heat; heats of reactions are experimentally determined in the calorimeter (Petrucci et al., 2011). Calorimeter also is the devise used for measuring the change in temperature and which a chemical and physical reactions process occurs in isolation. Thus, no heat enters or leaves the calorimeter allowing the heat flow of the process to be measured by determining the change in temperature (Bissonnette, et al., 2014). Heat capacity of a substance is the amount of heat required to raise the temperature of an object. The heat capacity also depends on whether the heating occurs at the constant volume, or at constant pressure (Petrucci et al., 2011). The specific heat of a substance is the heat necessary to raise the temperature of one gram of a substance. To find the heat, q, required to raise the temperature of a sample, multiply the specific heat of the substance by the mass, m, in grams and the change in temperature. Delta temperature means the difference in temperature final and temperature initial (Bissonnette et al., 2014). The equation to this determine the specific heat capacity or the mass, or temperature is defined as H=q=msor H=q=CT. Some examples of measurements that can be made by calorimetric work determining the heat capacity of an object, determining the specific heat of a metal and determining the enthalpy of reactions. Heat is lost by the hot water and gained by both the cold water and the calorimeter, thus the equation for this would be Ccalorimeter T= (msT)hot water – (msT)cold water. Ccalorimeter in the equation is the heat capacity of the calorimeter. The temperature is obtained from both the cold and hot waters. The mass of either hot water or cold water is determined by weighting. Neutralization of strong electrolytes involves strong electrolytes are completely dissociated into ions in diluted solutions. In this lab both the base and acid were strong electrolytes. The heat of neutralization for all reactions involving strong electrolytes will be constant and the same amount of heat will be formed (Petrucci et al., 2011).
Procedure
The experimental procedure used for this experiment was outlined in the CHEM 120L lab manual, experiment #4. All steps were followed without deviation
Observations
Part A: Heat of dissolution of NaOH
Mass of calorimeter: 44.90g
Mass of NaOH used: 10.00g
Initial temperature before NaOH added: 23.5°C
Table 1: Temperature of water in the calorimeter with NaOH pellets
Time (s)
Temperature (° C)
0
23.5 °C
10
24.0 °C
20
26.0 °C
30
27.0 °C
40
28.0 °C
50
28.7 °C
60
29.0 °C
120
32.2 °C
180
33.2 °C
240
33.2 °C
300
33.0 °C
360
33.2 °C
420
33.2 °C
480
33.2 °C
540
33.0 °C
600
33.0 °C
660
33.0 °C
720
33.0 °C
780
33.0 °C
840
33.0 °C
900
33.0 °C
960
33.0 °C
1020
33.0 °C
1080
33.0 °C
1140
33.0 °C
1200
33.0 °C
1260
33.0 °C
1320
33.0 °C
1380
32.8 °C
1440
32.8 °C
Part B: Determining heat capacity of the calorimeter
Mass of calorimeter with 125ml heated water: 140.32g
Mass of calorimeter with 250ml deionized water (after reaction): 262.37g
Initial temperature of cool water: 24.0°C
Table 2: Heated deionized water and cool water added into calorimeter
Time (min)
Temperature (° C)
-1
47.0 °C
-2
46.0 °C
-3
46.0 °C
-4
45.8 °C
-5
44.0 °C
0
34.0 °C
6
33.0 °C
7
33.2 °C
8
33.0 °C
9
33.2 °C
10
33.2 °C
11
33.0 °C
12
33.0 °C
13
33.0 °C
14
33.0 °C
15
33.0 °C
