Guide Questions for All Experiments

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Guide Questions

Experiment 1

Calibration of the calorimeter:

1.Give the net ionic thermochemical equation of the reaction used to calibrate the calorimeter. a.Is the reaction endothermic or exothermic?
b.Which is the limiting reactant?
c.How much (in moles) limiting reactant was used?
d.How much heat was generated (or absorbed) by the reaction? 2.Relate the sign of the ΔT to the ΔH of the reaction used for calibration. 3.What is the heat capacity of the calorimeter? Relate its sign to the sign of the ΔT. 4.In the appendix, show the derivation to obtain the equation used to calculate the heat capacity of the calorimeter.

Determination of Heats of Reaction:

5.Give the net ionic equation for each reaction.
6.Determine the limiting reactant and the amount of the limiting reactant in each of the reaction performed. 7.Calculate for the theoretical and experimental enthalpy of each reaction. a.Determine whether the reaction is endothermic or exothermic. b.Give the %error of your experimental values.

8.Relate the sign of ΔT to the sign of the experimental ΔH. 9.For reactions 1 – 4, which pair gave the most and the least exothermic (or endothermic) reaction? Explain the observation. (Use both the theoretical and experimental values to answer this) 10.For reactions 5 and 6, which gave the most exothermic reaction? Why? (Use both the theoretical and experimental values to answer this) 11.For reactions 7 and 8, what are the solid products of the reaction? What is the theoretical yield of each? 12.Reaction 8 is a synthesis (combination) reaction. Using the theoretical ΔH of the reaction, deduce the relative magnitude of the energy of bond breaking and bond formation during the reaction. 13.In the appendix, show the equation used to determine the heats of reaction for reactions 1 – 6 and reactions 7 and 8.

14.Tabulate the possible sources of errors and their effect to the following parameters: ΔT, Ccal and ΔH. Accompany each with a reason.

Source of ErrorEffect on ΔTEffect on CcalEffect on ΔH
SourceEffect (Reason)Effect (Reason)Effect (Reason)

Experiment 2

1.Give the balanced equation for the observed reaction in the experiment. 2.Describe the physical properties of the products produced and relate it to the balanced equation of the reaction. 3.What is the (approximate) Gibb’s Free Energy of the reaction observed? Assume that the reaction temperature is about 1000K. Use the Ellingham diagram provided in the manual to calculate for this. 4.Why should the Mg ribbon be filed prior to use?

5.What factors contributed for the slow/delayed ignition of Mg ribbons? Explain how each retarded ignition. 6.What is the possible side reaction in the experiment? Give the balance chemical equation for this side reaction. 7.What is the theoretical combined mass of the products in the experiment? Compare this to the one obtained in the experiment. Account for any difference. 8.What are the possible sources of errors in the experiment? Explain their effect to the yield.

Experiment 3

Determination of Rate Law of the Reaction Between Thiosulfate and Hydronium Ion

1.Give the balanced chemical equation for the reaction under study. 2.Express rate in terms of the change in reactants and products with respect to time; d[]/dt. 3.Of the species involved in the reaction, which chemical species served to determine the “end” of the reaction? What is the physical manifestation of the “end of the reaction? 4.Explain why the rate of reaction was approximated to be equal to 1/t. 5.Discuss the significance of using beakers of the same diameter when the experiment was performed. Determine the effect of not using beakers of same diameter to the rate of the reaction. 6.Discuss the significance of using the same timer when measuring the time it takes for the reaction to be completed. Determine the effect of not using the same timer to the rate of the reaction. 7.Discuss the significance...
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