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Exp7-solubility-F07

# Exp7-solubility-F07 - 7 From your graph calculate ∆ Sº...

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76 Experiment 7 GSIs Name_________________________________ Report Sheet Your Name_________________________________ Partners_________________________________ ___________________________________ Table 1. Class titration data and calculation results (or instead attach data) Group Temp. (K) Volume HCl (L) moles of H 3 O + moles of OH - moles of B 4 O 5 (OH) 4 -2 Sample size (L) M B 4 O 5 (OH) 4 -2 (moles/L) K 1/T lnK 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Make a van’t Hoff plot of lnK vs. 1/T. Fit the data to a straight line and report the equation for the line and the R 2 value. Attach the graph to your report sheet. Calculations: 1. What temperature was your solution that you titrated in Kelvin? 2. Show a sample calculation for the determination of the number of moles of OH - in your titration.

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77 3. Show a sample calculation for the determination of the number of moles of B 4 O 5 (OH) 4 -2 in your titration. 4. Calculate the molarity of the dissolved tetraborate ion, B 4 O 5 (OH) 4 -2 (aq), in your starting solution. 5. Write the equilibrium expression for this reaction
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Unformatted text preview: 7. From your graph, calculate ∆ Sº in J/mol•K. 8. From your graph, calculate ∆ Hº in kJ/mol. 9. Calculate ∆ Gº in kJ/mol for 30ºC. [ ] (l) O H 8 (OH) O B Na 2 (s) O H 8 (OH) O B Na 2 2 4 5 4 eq 2 4 5 4 2 + + ⎯→ ← ⋅ − + 78 Results and Discussion: 10. What does the term “standard conditions” mean? 11. What does the value of ∆ G ° at tell you about K sp at 30 ° C? 12. Under standard conditions does the solvation reaction favor products or reactants? 13. If ∆ G ° is positive (it should be), why does some of the borax still dissolve at room temperature? (Hint: what is the difference between ∆ G and ∆ G ° ?) 14. Does your value for ∆ H ° suggest that the solvation of borax is endothermic or exothermic? 15. Explain why this result is consistent with the observation that more borax dissolved at higher temperatures....
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