Chem Lab Lecture4

# Chem Lab Lecture4 - You will vary the volumes of NaClO and...

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Stoichiometry 1 of 5 Stoichiometry: Method of Continuous Variations The following reaction is exothermic: aNaClO + bKI products + a and b are: When the two reactants are combined in the true stoichiometric ratio: The heat liberated by the reaction is absorbed by the surroundings. The temperature change of the surroundings ( T) is thus an indication of the amount of heat liberated.

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Stoichiometry 2 of 5 You will perform this reaction 9 times. Each time you will vary the mole amounts of each reactant. You will measure T for each reaction to find the mole ratio that corresponds to the largest temperature change. The NaClO and KI solutions you prepare will be equal in concentration: NaClO (bleach): KI:
Stoichiometry 3 of 5 Since the concentrations of the two solutions are equivalent, volumes can be used in place of moles: Mole fraction of NaClO =

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Unformatted text preview: You will vary the volumes of NaClO and KI in each experiment: Volume NaClO (mL): Volume KI (mL): The total volume is always: Stoichiometry 4 of 5 Put NaClO in the polystyrene cup nested in a 250 mL beaker; measure the temperature with the temperature probe: Measure the temperature of the KI solution (rinse temperature probe first!) If the two initial temperatures are not the same, calculate a weighted average using: This is your T initial . Add KI to the cup with the NaClO and stir with the temperature probe. Record the highest temperature reached. This is your T final . Stoichiometry 5 of 5 Graph: Draw the two best straight lines and note the point where the two lines cross. This corresponds to the mole fraction of NaClO that gives the highest temperature change and is therefore used to calculate a and b. NOTE:...
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## This note was uploaded on 03/19/2008 for the course CHEM 1045 taught by Professor Pgamateis during the Spring '08 term at Virginia Tech.

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Chem Lab Lecture4 - You will vary the volumes of NaClO and...

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