Thermochemistry Lab

Purpose:
The purpose of the experiment is to calculate the enthalpy change occurring in the first of reaction of sodium hydroxide with hydrochloric acid and sodium hydroxide with ammonium chloride. Using Hess’ Law and the results for the enthalpy change of the first two reactions should give the enthalpy change of the third reaction of ammonia with hydrochloric acid.

Procedure:
Part 1:
Construct a calorimeter of two nested stereophony cups where the cover has a hole to fir a thermometer. Measure 50ml distilled water at room temperature into the calorimeter. Measure the temperature. Heat 75ml of distilled water to 70 degrees Celsius and pour it into the calorimeter. Record the temperature change every 20 seconds for 3 minutes.
Part2:
Find the average initial temperature of sodium hydroxide and hydrochloric acid. Determine the temperature change occurs when you mix 50ml of 2M of each solution using a magnetic stirring motor. Record the temperature every 20 seconds for 3 minutes. Repeat this process for the other two reactions.

Data and Calculations:
|Time (seconds) |Temperature (C) |
|0 |70 |
|20 |45.5 |
|40 |45 |
|60 |45 |
|80 |44.8 |
|100 |44.5 |
|120 |44.5 |
|140 |44.1 |
|160 |44 |
|180 |43.8 |

Temperature Changes in Water
|Time (seconds) |Temperature (C) |
|0 |70 |
|20