Using the data from Part C, calculate the [OH?] in the saturated Ca(OH)2 solutio
ID: 1064956 • Letter: U
Question
Using the data from Part C, calculate the [OH?] in the saturated Ca(OH)2 solution. Determine the [OH-]for each trial and an average and standard deviation for all three trials. NaOH concentration not given.
Pic 1- Procedure of titration of HCl and Ca(OH)2
Pic 2- Amount of HCl required for each Titration trail
Pic 3- Process to make standarized HCl solution (step 1) (I think this is how you calculate HCl concentration but I'm not sure)
Part C- Titration of Saturated Ca(oHU2 Solution 1. The saturated Ca(oH) solution should have settled by now. Take care not to stir up any of the solid from the bottom. Set up a funnel with a clean piece of filter paper and a flask to catch the filtrate. 2. Using a plastic disposable pipet, draw the solution off the top of the saturated Ca(oH)2 solution and transfer to the funnel for filtration. Collect 35-40 mL of the filtrate and cover it. If the filtrate is still cloudy ltration. 3 3. Using a volumetric pipet, place 10.00 mL of the filtrate into a clean 50 mL Erlenmeyer flask. Add drops of bromothymol blue indicator and titrate with the Hol. Record the initial and final buret volume readings to the nearest 0.01 mL. Repeat the titration twice for a total of three trials 4. Your flasks and volumetric pipets must be thoroughly cleaned with soap and warm water and rinsed before continuing to the next part of the procedure. Contamination will significantly alter the results in the next section of the lab procedure.Explanation / Answer
You haven’t mentioned the molar concentration (molarity) of either NaOH or HCl; however, for simplicity purpose, let us assume the molar concentration of HCl is 0.1 M.
Write down the balanced stoichiometric equation:
Ca(OH)2 (aq) + 2 HCl (aq) -------> CaCl2 (aq) + 2 H2O (l)
Moles Ca(OH)2 = moles Ca2+ = 2*moles OH- = 2*moles HCl.
Therefore, moles OH- = moles HCl.
Trial 1:
Initial reading of burette: 0.0 mL
Final reading of burette: 7.50 mL
Volume of HCl consumed = 7.50 mL
Moles of HCl used = (7.50 mL)*(1 L/1000 mL)*(0.1 mol/L) = 0.00075 mol.
Moles of OH- titrated = 0.00075 mol.
Volume of Ca(OH)2 = 10.00 mL.
Molar concentration of OH- = (0.00075 mol)/(10.00 mL)*(1 L/1000 mL) = 0.075 mol/L = 0.075 M
Trial 2:
Initial burette reading: 0.0 mL
Final burette reading: 7.12 mL
Volume of HCl consumed = 7.12 mL
Moles of HCl used = (7.12 mL)*(1 L/1000 mL)*(0.1 mol/L) = 0.000712 mol.
Molar concentration of OH- = (0.000712 mol)/(10.00 mL)*(1 L/1000 mL) = 0.0712 M
Trial 3:
Initial burette reading: 0.0 mL
Final burette reading: 6.95 mL.
Volume of HCl consumed = 6.95 mL
Moles of HCl used = (6.95 mL)*(1 L/1000 mL)*(0.1 mol/L) = 0.000695 mol.
Molar concentration of OH- = (0.000695 mol)/(10.00 mL)*(1 L/1000 mL) = 0.0695 M
Average molar concentration of OH- = (0.075 + 0.0712 + 0.0695)/3 M = 0.0719 M (ans).
Calculation of standard deviation:
Uncertainty in volume = 0.01 mL.
Nothing is mentioned about the uncertainty in concentration of HCl; will need that information to calculate the uncertainty in concentration of OH-.
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