Microsoft Word - NaOH Standardization Report.docx
Standardization of NaOH
Name:
#1). Molarity of KHP: _________________ Volume of KHP: _________________
#2). How many moles of KHP are in the flask? Show your work
#3). How many grams of KHP is in the flask? (MW = 204.22g/mol) Show your work.
#4). Initial pH of KHP Solution: ________________
#5). Initial [H+] Concentration in KHP Solution. Show your work
#6). Desired NaOH Concentration: _______________
#7). You are preparing 250.00mL of your desired concentration from a 1M stock solution of
NaOH. How many mL of 1M NaOH is needed? Show your work.
#8). Show your work for the Molarity determination for Trial #1.
Trial #1 Trial #2 Trial #3
Initial Burette
Reading
Final Burette
Reading
Volume of NaOH
Delivered
Molarity of
NaOH
#9). What is the average Molarity of your NaOH solution? Show your work.
#10). What is the deviation for each of your three trials? Show your work.
#11). What is the average deviation of your Molarity? Show your work.
#12). What is your percent e
or based on the theoretical concentration (the concentration
you selected to prepare)? Show your work.
#13). What is the net ionic equation for this reaction?
Questions
#14). If some of the Potassium Hydrogen Phthalate spills out of the flask without your
knowledge, how will that affect the calculated Molarity of the Sodium Hydroxide? Explain
your answer.
#15). Using your calculated average molarity, what volume would be needed to titrate
25.00mL of a 0.500M sample of Phthalic Acid. Keep in mind this is a diprotic molecule. Show
your work.
1 Molarity of KHP:
Volume of KHP:
4 Initial pH of KHP Solution:
6 Desired NaOH Concentration:
Text1:
Text2:
Text3:
Text4:
Text5:
Initial Burette Reading:
Final Burette Reading:
Volume of NaOH Delivered:
Molarity of NaOH:
Initial Burette Reading2:
Final Burette Reading2:
Volume of NaOH Delivered2:
Molarity of NaOH2:
Initial Burette Reading3:
Final Burette Reading3:
Volume of NaOH Delivered3:
Molarity of NaOH3:
Text6:
Text7:
Text8:
Text9:
Text10:
Text11:
Text12:
Microsoft Word - Online Titration Procedure.docx
NaOH Standardization Procedure
Navigate to the following website: http:
chemcollective.org/vla
101
Obtaining Supplies
Under the Stockroom Item on the Left Side, under the Solutions Tab, select the following to add to the
workbench
~1M NaOH
Distilled Water
0.500M KHP
Phenolphthalein
Under the Stockroom Item on the Left Side, under the Glassware Tab, select the following to add to the
workbench
250mL Volumetric Flask
Burette (listed under “other”)
A few beakers (you can always get more)
Transfer Pipette
Preparing the Diluted Solution
Add the ~1M NaOH solution, distilled water, and a 250mL Volumetric Flask from the Stockroom
Calculate what volume of NaOH is needed to prepare your desired solution. Choose one of the following
0.300M 0.400M 0.600M 0.700M
Drag the NaOH to the Volumetric Flask, and precisely add this calculated amount.
Drag the distilled water and precisely add an amount below what is needed,
Drag the distilled water to an empty beaker and add some amount (~100mL)
Drag the transfer pipette to the beaker and use it to withdraw until the pipette is full
Drag the full pipette to the volumetric flask and slowly “pour” into the flask until the volume is exactly at
the 250.00mL mark. If you go over this mark, you must remake the solution.
NaOH Standardization Procedure
Preparing the Titration
Add the Phenolphthalein and 0.500M KHP (Potassium Hydrogen Phthalate) from the Stockroom
Record the pH of the KHP solution. This is listed on the left side when you click on the Flask
On the workbench area, drag the Phenolphthalein to the 0.500M KHP and add 1 mL
On the workbench area, drag your volumetric flask containing your NaOH solution, to the Burette and
add 50mL
You will notice it will not be at exactly the 0.00mL mark. This is because burettes are designed to
measure how much volume leaves the burette, not how much is inside it.
Add additional NaOH until the reading on the buret is 0.00mL
Performing the Titration
On the workbench area, drag the Burette to the 0.500M KHP flask.
Click on the “Realistic” tab, and click hold to pour.
As the button is held down, this will dispense the NaOH to the flask.
Dispense the NaOH into the flask until the solution just begins to turn red/pink and record the volume
eading on the buret.
Repeat the titration with two additional flasks of KHP. You will need to refill your buret at least once, but
it does not need to be filled to exactly 0.00mL
Moles & Molarity
Standardization of naoh
Introduction to acids & bases
Every reaction performed in water (and even some which are not) will have some amount of acid and base present in the solution
In aqueous solutions, the acid and base come from the equili
ium reaction of water itself
Depending on how the reaction interacts with itself and the water around it, the overall amount of Acid and Base will shift
pH is a measurement scale used to co
elate the concentration of Acid [H+] in a solution
The ph scale
pH [H+] Concentration
-1 10M
0 1M
1 0.1M
2 0.01M
3 0.001M
4 0.0001M
5 0.00001M
6 0.000001M
7 0.0000001M
8 0.00000001M
9 0.000000001M
10 0.0000000001M
Basic
Neutral
Acidic
pH = 0
pH = 7
pH = 14
pH is a logarithmic scale seen on the left and predominantly covers concentrations below 1M, though it can still be used for higher concentrations as well
The typical pH scale ranges from 0 to 14, with lower numbers being acidic (high [H+]) and larger numbers being basic (low [H+])
Pure water has a pH of 7 based on the equili
ium constant of water (Kw)
pH 7 is considered the exact neutral point, however any value close to 7 would also be considered neutral (6.8, 7.2, etc.)
pH is an easier number to work with on a regular basis, but can still be used to determine the exact concentration of Acid
Performing titrations
Titrations are the careful addition of one reactant to another by adding small amounts at a time
By doing so, the exact moment where the reaction is complete can be determined
Titrations are typically done to determine an unknown concentration of something by adding a precisely known concentration of the other reactant
A number of different types of chemistry can be studied looking at titrations, most frequently seen in acid
ase chemistry
Under-
Titrated
Ove
Titrated
Exact
Titrations are very exact measurements using burets and very precise concentrations
Titrations a complete when a single drop from the buret will cause a color change
Burettes
The value listed on the buret is recorded
The volume delivered is the Final reading minus the Initial reading
indicators
Most acids are clear and colorless, as are most bases. When they react they form a clear and colorless product
An indicator is a chemical that is added to a solution that undergoes a visual change at a specific point to know when a reaction is completed
These typically do not interact with the overall reaction, but as more products are formed, they will be in equili
ium with them and change their appearance
Many indicators display specific colors based on the concentration of H+ (pH) of a solution
Phenolphthalein
Colorless at low pH
Pink at high pH
standardization
This experiment is the standardization of a NaOH solution you prepare.
In the experiment, you prepare a solution from a 1M stock solution of NaOH, and based on significant figures, the precision of your solution could only have 1 sig fig
To standardize the solution (making the concentration known to a much higher level of precision), you will titrate your solution into a very accurate known amount of the other reactant
Your final calculated molarity should have 3 significant figures as opposed to only 1
Standardization is used in laboratory settings a lot to both accurately and precisely know the concentration of a solution
Standardization of naoh – Virtual lab Experiment
Where to Go?
Direct Simulation Link: http:
chemcollective.org/vla
101
Reaction
Potassium Hydrogen Phthalate (KHP)
+ OH-
+ H2O
Phthalate Ion
The Potassium Hydrogen Phthalate ion dissociates in water due to its solubility
The Potassium Ion and the acidic Hydrogen Ion
eak off
The Acidic Hydrogen undergoes the reaction with Hydroxide to form water
Net Ionic Reaction
Monoprotic vs polyprotic
Phthalic Acid
Monoprotic Acids
Hydrochloric Acid (HCl)
Nitric Acid (HNO3)
Acetic Acid (CH3COOH)
Potassium Hydrogen Phthalate
Diprotic Acids
Triprotic Acid
Sulfuric Acid (H2SO4)
Ca
onic Acid (H2CO3)
Phthalic Acid
Oxalic Acid
Phosphoric Acid (H3PO4)
How many moles of hydroxide will react?
Net Ionic Reaction
Phthalate Ion
calculations
Preparation of Solution
Determining Accurate Molarity
M1 = Stock Solution Concentration (1 molar)
V1 = The volume of Stock Solution needed
M2 = The molarity that you choose to prepare
V2 = The Final Volume of your solution flask (250.00mL)
The Potassium Hydrogen Phthalate (KHP) solution is very known to high levels of precision
KHP Volume for Each Trial = 25.00mL
KHP Concentration for Each Trial = 0.500M
KHP is monoprotic, meaning that for every mole of KHP, it will react with one mole of Base
My determining the volume needed from the buret to deliver that number of moles, you can determine the molarity of the NaOH solution in the buret
http:
chemcollective.org/vla
101
The stimulation link