Presentation on theme: "Determination of K, ΔG˚, ΔH˚, and ΔS˚ Borax Na 2 B 4 O 7 ·10H 2 O (Sodium Tetraborate Decahydrate )"— Presentation transcript:
Determination of K, ΔG˚, ΔH˚, and ΔS˚ Borax Na 2 B 4 O 7 ·10H 2 O (Sodium Tetraborate Decahydrate )
Quiz Question # 4 Look at following equation to write down your Ksp:
First things first… Safety: Put bags away Goggles Lab Jacket Turn in Lab Reports LAB!
Gibbs Free Energy (ΔG), Enthalpy (ΔH), and Entropy (ΔS) y=m x + b
Changes in Procedure Each group does one temp (assigned). 2 trials. Add 2 scoops of borax and 75 mL of distilled water to a beaker Heat the solution (<50 °C) so that the solution is saturated. Heat slowly! No need to speed up the heating process. Once slightly above assigned temperature, take off hotplate. If all the solid has dissolved, add some more borax to beaker. Pour 5 mL of the solution into a graduated cylinder once the solution is at the desired temperature. Record volume to tenths place. Be sure to record temperature to the tenths place.
Procedure (continued) Add the 5 mL of solution to an Erlenmeyer with 50 mL distilled water, 5 drops bromocresol green, mix thoroughly, add a little distilled water to rinse the graduated cylinder into the Erlenmeyer (Quantitative Transfer) Titrate with HCl (clean/rinse buret and fill w/ ~20 mL HCl) REPEAT! The above steps for two more titrations. DO NOT try to prepare three samples at once, unless you can guarantee the temperature of the borax solution will not change dramatically!
Turn in class: Pre-lab, filled in data tables, observations Type in you and your partner’s data in class computers on opened excel spreadsheet Trial 1 Name[HCl]Temp Volume Borax Solution Used Volume HCl used (M) ( ° C) (mL) Jack and Jill
Formal Lab Report – due in two weeks Table 1, 2 – for each trial solve for: Table 4 – average the trials to find (for each temp): Temp (K) mol HCl used mol borate ion [Borax] (M) KsplnKsp ΔG (kJ/mol ) Temp (K)KsplnKsp ΔG (kJ/mol ) 1/T
Data Tables (con’t) Temp (K) ΔG (kJ/mol) Table 5 – use ΔH and ΔS to solve for ΔG for each Temp