Heats of Reaction Lab Report Essay

955 Words Mar 1st, 2013 4 Pages
Heats of Reaction Lab Report

Purpose: To measure the heats of reaction for three related exothermic reactions and to verify Hess’s Law of Heat Summation.

NaOH(s) ( Na+(aq) + OH-(aq) ΔH = -10.6kcal/mol
NaOH(s) + H+(aq) + Cl-(aq) ( H2O + Na+(aq) + Cl-(aq) ΔH = -23.9kcal/mol
Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) ( H2O + Na+(aq) + Cl-(aq) ΔH = -13.3kcal/mol

Background: Energy changes occur in all chemical reactions; energy is either absorbed or released. If energy is released in the form of heat, the reaction is called exothermic.
If energy is absorbed, the reaction is called endothermic.

Materials: spatula sodium hydroxide pellets (NaOH) 1 Styrofoam cup 1.0 M sodium hydroxide (NaOH) 1 100-mL graduated
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CAUTION: NaOH is extremely corrosive. c. Measure and record the temperature of the HCl solution in the foam cup. Add the NaOH pellets to the acid solution and stir gently until the solid is dissolved. Measure and record the highest temperature reached by the solution during the reaction. Reaction 3: a. Place the plastic foam cup inside a 400mL beaker. Measure 50mL of 1.0M HCl into the cup. Rinse the graduated cylinder and fill with 50mL of 1.0M NaOH. b. Measure and record the temperature of the HCl solution (in the cup) and the NaOH solution (in the cylinder) to the nearest 0.5ºC. Rinse the thermometer between measurements. c. Pour the NaOH solution into the foam cup. Stirring the mixture gently, measure and record the highest temperature reached.

Data Table 1: Observations
| |Reaction 1 |Reaction 2 | |Reaction 3 |
|Volume of Water (ml) | |------------ |Volume 1M HCl (ml) | |
|Volume 0.5M HCl (ml) |------------- | |Initial Temp HCl ˚C | |
|Mass of NaOH (g) | | |Volume 1M NaOH (ml) | |
|Initial Temp ˚C

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