User:Xenomancer/LLE Titration Evaluation/KHP Soln Prep

Preparation of KHP standard solution

Materials

Chemicals

1. ~22 g potassium hydrogen phthalate (KHP), ACS or USP grade
2. ~1200 mL distilled water (DI)

Labware

1. 1× metal spatula
2. 1× 100 mL glass beaker
3. 1× 500 mL glass beaker
4. 1× glass stiring rod
5. 1× medium glass liquid transfer funnel
6. 1× 1000 mL glass volumetric flask w/ stopper, grade A
7. 1× 1 L amber glass bottle
8. 1× blank label (for glass bottle)
9. 1× permanent marker (for label)

Instrumentation

1. 1× analytical mass scale

• capacity ≥ 25 g
• uncertainty ($\,\sigma _{scale}$) ≤ ±0.5 mg

Procedure

1. Weigh out a sample of KHP into the 00 mL glass beaker.
   1. Place the 100 mL glass beaker on the analytical scale.
   2. Zero the analytical scale to neglect the tare weight of the 100 mL beaker.
   3. Remove the 100 mL glass beaker from the analytical scale.
   4. Using the metal spatula, transfer roughly 20 grams of KHP to the 100 mL glass beaker.
   5. Place the 100 mL glass beaker back on the analytical scale.
   6. Wait for the analytical scale to settle on a fixed reading.
   7. Record the exact mass of KHP $\left(\,m_{KHP}\right)$.
2. Quantitatively transfer the weighed out KHP from the 100 mL glass beaker to the 1000 mL volumetric flask using DI.
   1. Using the medium glass luid transfer funnel
3. Bring the volumetric flask to volume with DI.
4. Seal the volumetric flask with its stopper and mix well.
   1. Mixing is satisfactorily completed 3 minutes beyond complete dissolution of the KHP.
   2. Be sure to invert the volumetric flask several times while shaking to agitate the neck volume of the flask.
5. Transfer the solution from the 1000 mL volumetric flask to the 1 L amber glass bottle.
   1. Remove the stopper form the volumetric flask.
   2. Ensure that the 1 L amber glass bottle is clean.
      1. If the amber glass bottle is visibly dirty, rinse it with DI.
   3. Transfer a small aliquot (10 mL to 20 mL) of solution from the volumetric flask to the amber glass bottle.
   4. Close the amber glass bottle and swirl the solution around, covering all surfaces, to rinse the container.
   5. Open the amber glass bottle and empty the contents into the appropriate waste container.
   6. Repeat the last three steps two more times.
   7. Carefully transfer the solution to the amber glass bottle.
6. Label the bottle with the appropriate information.
   1. Solution name: "$\left({\text{num}}\pm {\text{err}}\right){\text{M}}$ KHP Standard"
   2. Date prepared: "MM/DD/YYYY"
   3. Name of preparer: "FirstInitial LastName"

Data analysis

The concentration of KHP in the standard can be found via straight forward dimensional analysis.

$C_{KHP}={\frac {m_{KHP}}{{\overline {M}}_{KHP}}}\times {\frac {1}{V_{flask}}}={\cfrac {m_{KHP}}{204.22{\cfrac {g{\text{KHP}}}{mol{\text{KHP}}}}\times 500mL\times {\cfrac {1L}{1000mL}}}}={\frac {m_{KHP}}{102.11g{\text{KHP}}}}{\text{M}}$ (1)

Error analysis

Using the standard differential error formula

$\,\sigma _{f}^{2}=\sum _{i=1}^{n}{\left({\frac {\partial f}{\partial x_{i}}}\right)^{2}\sigma _{x_{i}}^{2}}$ (2a)

or

$\,\Delta f^{2}=\sum _{i=1}^{n}{\left({\frac {\partial f}{\partial x_{i}}}\right)^{2}\Delta x_{i}^{2}}$ (2b)

and the measurement/instrument uncertainties

$\,\sigma _{V_{flask}}=0.20mL\rightarrow \Delta V_{flask}=\pm 1.960\times 0.20mL\rightarrow \Delta V_{flask}=\pm 0.392mL$

$\,\Delta m_{KHP}=\pm 0.0001g$

the concentration uncertainty for KHP is given by

$\,\Delta C_{KHP}=\pm {\sqrt {\left({\frac {\partial C_{KHP}}{\partial m_{KHP}}}\right)^{2}\left(\Delta m_{KHP}\right)^{2}+\left({\frac {\partial C_{KHP}}{\partial V_{flask}}}\right)^{2}\left(\Delta V_{flask}\right)^{2}}}$ (3)

where

${\frac {\partial C_{KHP}}{\partial m_{KHP}}}={\frac {1000{\frac {mL}{L}}}{{\overline {M}}_{KHP}V_{flask}}}$ (4)

and

${\frac {\partial C_{KHP}}{\partial V_{flask}}}=-{\frac {m_{KHP}\times 1000{\frac {mL}{L}}}{{\overline {M}}_{KHP}V_{flask}^{2}}}$ (5)

Substituting for the partial derivatives yields

$\,\Delta C_{KHP}=\pm {\frac {1000{\frac {mL}{L}}}{{\overline {M}}_{KHP}V_{flask}}}{\sqrt {\Delta m_{KHP}^{2}+{\frac {m_{KHP}^{2}\Delta V_{flask}^{2}}{V_{flask}^{2}}}}}$ (6a)

The simplified form for the uncertainty using the example data is

$\,\Delta C_{KHP}=\pm {\sqrt {5.89516\times 10^{-11}g^{-2}\times m_{KHP}+9.591\times 10^{-13}}}{\text{M}}$ (6b)

which means the concentration is fully given by the equation

$\,C_{KHP}={\frac {m_{KHP}}{{\overline {M}}_{KHP}V_{flask}}}\pm {\frac {1000{\frac {mL}{L}}}{{\overline {M}}_{KHP}V_{flask}}}{\sqrt {\Delta m_{KHP}^{2}+{\frac {m_{KHP}^{2}\Delta V_{flask}^{2}}{V_{flask}^{2}}}}}$ (7a)

or

$C_{KHP}={\frac {m_{KHP}}{102.11g}}\pm {\sqrt {5.89516\times 10^{-11}g^{-2}\times m_{KHP}+9.591\times 10^{-13}}}{\text{M}}$ (7b)

Data and results

Data Log

Date (dd/mm/yyyy)	Experimenter (ID)	Mass of KHP (g)	Moles of KHP (mol)	Flask Volume (mL)	Concentration of KHP (mol/L)	Comments
01/01/2011	AAA	20.0000 ± 0.0001	0.09793360102 ± 0.00000049	1000.00 ± 0.39	0.097934 ± 0.000019	This is example data. Replace it with the first completed run.