Purpose: For this experiment, my partner and I will complete three different parts. For part I, we will determine which indicator we will use for part II and III. We will test three indicators, Boomcreiol, Methyl, and 1% Phenolphthalein. For part II you will take the indicator you have chosen and use titrations with NaOH to see how much it takes to neutralize HCl. For part III you will do the same thing but to see how much it takes to neutralize H₂SO₄.
Procedures: My partner, Marisa, and I will work together to complete this experiment. We will first determine which indicator we will use for the titrations in part II and III. Once we determine that, we use it with the sets of titrations with NaOH. Both Marisa and I will equally do work for both parts I, II, and III.
Part I - Acid-Base Titrations with Chemical Indicators
We obtained a 24 chem well-plate, 40 mL of HCl, and 100 mL of NaOH.
We cleaned out a buret with the base, NaOH.
We then obtained three different indicators: Boomcreiol green, Methyl orange, and 1% Phenolphthalein.
Using the well-plate we sorted the indicators into 3 rows.
To one well of each row of indicator, we added 5 drops of HCl, 5 drops of distilled water, and 5 drops of NaOH.
We determined which indicator we would use for part II and III: 1% Phenolphthalein.
Part II - Titration of unknown HCl with standardized NaOH using a Chemical Indicator
We took a 10.00 mL pipette and cleaned it with HCl.
We filled 10.00 mL of HCl and put it in the 125 mL flask, plus two drops of indicator.
We preformed 3 different titrations to determine how long it would take to neutralize the HCl.
Part III - Titration of unknown H₂SO₄ with standardized NaOH using a Chemical Indicator
We took a 10.00 mL pipette and cleaned it with H₂SO₄.
We filled 10.00 mL of H₂SO₄ and put it in the 125 mL flask, plus two drops of indicator.
We preformed 3 different titrations to determine how long it would take to neutralize the H₂SO₄.
Data and Results: The data tables I will display are also found in my carbonless copy lab notebook.
Results for Part I
Table 1. Selection of Chemical Indicators:
(HCl 5 drops)
(Water 5 drops)
(NaOH 5 drops)
This best indicator to use from Table 1 would be the 1% Phenolphthalein. We’re using NaOH with both of our titration samples, so we would like the NaOH to be the different color from the rest.
Results for Part I
Concentration of NaOH: 0.1236 M
Table 2. Titrations for Part II:
Initial Vol. NaOH (mL)
Final Vol. NaOH (mL)
Vol. NaOH used (mL)
Concentration of HCl (M)
Example calculations of moles of NaOH: moles of NaOH = (volume NaOH in L)*(M of NaOH) = (0.01199 L)*(0.1236) = 1.48 x 10⁻² mol NaOH
Example calculation of moles of HCl: moles of HCl = moles NaOH used = 1.48 x 10 ⁻² moles HCl
Example calculation of concentration of HCl: concentration of HCl = (moles HCl) / (volume HCl in L) = (1.48 x 10 ⁻² moles) / (0.01 L HCl) = 0.1482 M HCl
Average concentration of HCl with standard deviation: Avgerage concentration of HCl = (0.1482 M) + (0.1458 M) + (0.1481 M) / 3 = 0.1474 M HCl Standard deviation of HCl: 0.1482 M - 0.1474 M = (0.0008 M)² = 0.00000064 M 0.1458 M - 0.1474 M = (-0.0016 M)² = 0.00000256 M 0.1481 M - 0.1474 M = (0.0007 M)² = 0.00000049 M (0.00000064 M + 0.00000256 M + 0.00000049 M) = 0.00000369 M / 3 = 0.00000123 M = √(0.00000123 M) = σ = 1.11 x 10 ⁻³ M HCl Percent error of HCl: % error = (⎪Approx. Value - Exact Value⎪/⎪Exact Value⎪) x 100 % = (⎪0.1474 M - 0.1458⎪/⎪0.1458⎪) x 100 % = 1.10 %
Table 3. Titrations from part III:…