Determining an enthalpy change of the neutralisation reactions

Aim: To determine the enthalpy change ΔH and the heat of reaction Q for two neutralisation reactions.
• Scales
• Stopwatch
• Graduated cylinder
Procedure:
1) Make a calorimeter using 2 plastic cups, a cover and a stirrer.
2) Measure the calorimeters weight (m1).
3) Pour a little of the base (NaOH) into the graduated cylinder.
4) Using the graduated cylinder add 20.0 ml of the base to the calorimeter
5) Measure the weight of the base (m2).
6) Insert a thermometer through the lid. Make sure that the thermometer bulb is below the solution’s surface and record the temperature (t1).
7) Pour a small quantity of acid (HCl) into the graduated cylinder.
8) Measure 20.0 ml of acid in the graduated cylinder and measure acid’s weight (m3).
9) Insert a thermometer and record the temperature (t2).
10) When the temperature is within 1.0 °C of that of the base solution, add the base to the acid.
11) While stirring gently with the thermometer, measure and record the temperature immediately after mixing and then every 30 seconds at least for 5 minutes or until the temperature reaches a maximum (t3) and declines for two successive time intervals.
12) Be sure to record the maximum temperature even if it occurs at mid-interval.
13) Empty the calorimeter, rinse and dry all parts carefully, and allow it to return to room temperature.
14) Repeat the same experiment two more times.
15) Repeat steps 1-6 with base (NaOH) and acid (HNO3).
Hypothesis:
Acid + Base -> Water + Salt
HCl(aq) + NaOH(aq) -> H2O(l) + NaCl(aq)
HNO3(aq) + NaOH(aq)-> H2O(l) + NaNO3(aq)
The enthalpy change of this reaction should be negative, because during the neutralisation reaction...

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