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13 Dec 2019

1.) average number of moles of NaOH dispensed
2.)average concentration of the acid (mol/L)

3,) Based on your coarse titration volume, do you expect the acetic acid solution to have a higher or lower concentration than the NaOH solution?

higher could you please tell me if number 3 is right

please help with these 2 questions

Part 1: Prepare the NaOH Solution

Lab Results

How many mL of water were used to prepare the NaOH solution?

200mL

Data Analysis

Calculate the molarity of the NaOH solution. The molar mass of NaOH is 39.997 g/mol.

0.1M

Calculate the amount of benzoic acid to be neutralized by 20.00 mL NaOH solution, in both moles and grams. The molar mass of benzoic acid is 122.12 g/mol.

1.207 g

Part 2: Perform a Coarse Titration

Lab Results

Record the following data from your course titration in the table below.

mass of benzoic acid used (g) 0.26614g
pH of benzoic acid solution before titration 2.96
volume of NaOH in the burette before titration (mL) 50.0mL
volume of NaOH in the burette after titration (mL) 28.89mL
volume of NaOH dispensed in the titration (mL) 21.11mL

Data Analysis

How do you expect your coarse titration volume to compare to your fine titration volumes?

I expect the values to be a little off from each other since in the first titration we let out a lot at a time and didnt slowly do the titration. should only be off by a few mL.

Part 3: Perform Fine Titrations

Lab Results

Record the volume of NaOH solution dispensed in the 3 fine titrations.

20 mL dispenced ,20.34mL, 20.30mL

Data Analysis

Calculate the average concentration of the NaOH solution, using the average volume of NaOH solution dispensed in the 3 fine titrations. Report your answer using enough significant figures to distinguish it from the expected concentration of 0.100 M.

V = (V1 + V2 + V3) / 3

V = (20.03 mL + 20.06 mL + 20.02 mL) / 3 = 20.04 mL

M = n / V = 0.00200 moles / 0.02004 L = 0.0998 M

Learning objective: Determine the concentration of a solution.

20.21= ----> 0.0999M

Experiment 2: Use the Standardized NaOH Solution to Determine the Concentration of an Acid

Part 1: Perform a Coarse Titration

Lab Results

What was the pH at the end point of the coarse titration?

3.87ph

Data Analysis

Based on your coarse titration volume, do you expect the acetic acid solution to have a higher or lower concentration than the NaOH solution?

higher

Part 2: Perform Fine Titrations

Lab Results

For the 3 fine titrations of the acid of unknown concentration, fill in the following data.

Titration #1 Titration #2 Titration #3
volume of acid (mL) 59.11 40.97 40.98
volume of NaOH dispensed (mL) 9.05 9.03 9.02

Data Analysis

Calculate the following quantities and record the data in the table below.

average volume of NaOH solution dispensed (mL) 9.03
average number of moles of NaOH dispensed
average concentration of the acid (mol/L)

Conclusions

Phenolphthalein is pink over the range of pH 8 – 12. Why was it a useful indicator of when the equivalence point was reached?

This was helpful because once I got to the ph of 7 I knew that I would be getting closer to the end point which would change the color to pink.

Suppose a student titrated a sample of monoprotic acid of unknown concentration using a previously standardized solution of NaOH.

volume of 0.125 M NaOH dispensed 24.68 mL
volume of acid solution 50.00 mL

Given the data in the figure above, what is the concentration of the unknown acid?

0.0617M

Lab NOTES:

ex1

Take sodium hydroxide from the Materials shelf and add 0.800 g to the beaker.

Take water from the Materials shelf and add 200 mL to the beaker.

Ph 2.96

inital volume in burett

inital volume 50ml

1.) volume43.78mL

volumes dispenced =6.22ml

2. volume =38.05

volume dispenced =11.95ml

3.)volume = 32.06

volume dispenced=17.94

4.28.89ml

volume dispenced=21.11ml

ph=10.95

--------------------------------------

Ex 2

inital ph= 2.96

volume30.33

dispence 20.05

1. volume 39.92ml

volume dispenced=10.08

2.volume 29.66

voiume dispence 20.34

final ph10.43

initial valume in burett 50ml

--------------------

ex3

final ph9.43

volume 30.28

volume dipenced=20.00

----------------------------------------------------------------------

2nd Ex

initial ph 3.11

volume 50

1. volume 48.95mL

dispenced 1.05mL

ph 3.87

2. volume 45.88

dispenced 4.12

ph 4.67

3 volume 42.99

dispenced 7.01

ph 5.29

4 volume 39.93

dispence 10.07

ph 11.45

--------------------

F1

final ph 9.99

volume 59.11

dispenced 9.05

F2

ph 9.59

volume 40.97

dispenced 9.03

f3

ph 9.50

volume 40.98

9.02

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Related questions

Lab Results 1.For your coarse titration record the following results. volume of NaOH solution in the burette at the start (mL) volume of NaOH solution in the burette at the end (mL) volume of NaOH solution dispensed (mL) volume of HCl solution in the flask (mL) Data Analysis 2.Calculate the molarity of the HCl concentration using your coarse titration results. Experiment 2: Perform a Fine Titration Lab Results 1.For your fine titration record the following results. volume of NaOH solution in the burette at the start (mL) volume of NaOH solution in the burette at the end (mL) volume of NaOH solution dispensed (mL) volume of HCl solution in the flask (mL) Data Analysis 2.Calculate the molarity of the HCl concentration using your fine titration results. Conclusions 1.What do you expect to happen if you forget to add phenolphthalein to the Erlenmeyer flask? 2.Suppose you had to titrate a solution of NaOH of unknown concentration with a solution of HCl of known concentration using phenolphthalein as an indicator. How will you determine the color change? 3.Suppose you titrated a sample of acetic acid (monoprotic acid) with a 0.125 M solution of NaOH. Given the data in the table below, what is the concentration of the acetic acid solution? volume of 0.125 M NaOH dispensed 22.40 mL volume of acetic acid solution used 15.00 mL volume of water added to the HCl solution 15.00 mL


Experiment 1: Standardize an NaOH Solution Using Benzoic Acid as Primary Standard

Part 1: Prepare the NaOH Solution

Take a 250 mL beaker from the Containers shelf and place it on the workbench.

Take sodium hydroxide from the Materials shelf and add 0.800 g to the beaker.

Take water from the Materials shelf and add 200 mL to the beaker.

Calculate the expected concentration of the sodium hydroxide solution. The molar mass of NaOH is 39.997 g/mol.

Calculate and record the expected mass of benzoic acid required to react with 20.00 mL of a 0.100 M sodium hydroxide solution. Record the mass of benzoic acid using three significant digits

Part 2: Perform a Coarse Titration

Take a clean Erlenmeyer flask from the Containers shelf and place it on the workbench.

Take water from the Materials shelf and add 100 mL to the Erlenmeyer flask.

Add the required mass of benzoic acid calculated in step 5 of part 1 to the Erlenmeyer flask. The 100 mL of water should be enough to dissolve the solid benzoic acid.

Take phenolphthalein from the Materials shelf and add 2 drops to the Erlenmeyer flask.

Take a pH meter from the Instruments shelf and place it into the flask. Record the initial pH of the solution.

Take a burette from the Containers shelf and place it on the workbench.

Take the prepared sodium hydroxide solution from the workbench and add 50 mL to the burette. Pass the mouse cursor over the burette and a gray tool tip will briefly display the total volume in the burette as well as the volume dispensed. Record these initial volumes.

Move the Erlenmeyer flask onto the base of the burette.

Perform a coarse titration, adding large increments of titrant (~ 2 mL) by pressing and holding the stopcock at the bottom of the burette for 1-2 seconds. Pause after each dispensation. Record the volume dispensed.

Check if the end point has passed. When the reaction reaches the end point, the solution changes color. Also, as sodium hydroxide is added to the benzoic acid solution, the pH increases.

Stop once you reach the end point. Record the volume dispensed and pH at which this occurs. Record both the last dispensed volume where the solution was colorless (right before the end point) and the first dispensed volume where the solution changed color. You will use the volume dispensed before the end point in the fine titration.

Discard the Erlenmeyer flask by dragging it to the recycling bin beneath the workbench.

Part 3: Perform Fine Titrations

Prepare an Erlenmeyer flask as described in steps 1 - 5 in part 2 of experiment 1.

Take sodium hydroxide solution from the workbench and refill the burette to a total volume of 50 mL. Record this initial volume.

Move the Erlenmeyer flask onto the base of the burette.

Click and hold the stopcock of the burette to quickly add the before the end point volume of sodium hydroxide determined in the coarse titration.

Add titrant in small increments, down to one drop at a time. This can be tedious, but if you click and hold you might miss the exact end point of the titration.

When the solution changes color, stop adding titrant. Record the pH and volume dispensed.

Clear your workstation by dragging the Erlenmeyer flask to the recycling bin.

Repeat the fine titration two more times, and record the results.

Calculate the concentration of the sodium hydroxide solution. The rest of the sodium hydroxide solution can now be used in further lab work as a secondary standard with a reliably known concentration equal to the average of the three titrations.

Experiment 2: Use the Standardized NaOH Solution to Determine the Concentration of an Acid

Part 1: Perform a Coarse Titration

Take an Erlenmeyer flask from the Containers shelf and place it on the workbench.

Take acetic acid #1 (unknown concentration) from the Materials shelf and add 25 mL to the flask.

Take phenolphthalein from the Materials shelf and add two drops to the flask.

Take a pH meter from the Instruments shelf and place it into the Erlenmeyer flask. Record the pH.

Take the NaOH solution from the workbench and refill the burette to a volume of 50 mL. Pass the mouse cursor over the burette and a gray tool tip will briefly display the total volume in the burette as well as the volume dispensed. Record these volumes.

Move the Erlenmeyer flask onto the base of the burette.

Perform a coarse titration, adding large increments of titrant (~ 2 mL) from the burette by pressing and holding the stopcock at the bottom of the burette. Pause after each dispensation. Record the volume dispensed.

Check if the end point has passed. When the reaction reaches the end point, the solution changes color. Also, as more sodium hydroxide is added to the acetic acid solution, the pH increases.

Stop once you reach the end point. Record the dispensed volume and pH at which this occurs. Record both the last dispensed volume where the solution was colorless (right before the end point) and the first dispensed volume where the solution changed color. You will use the volume dispensed right before the end point in the fine titration.

Clear your station by dragging the Erlenmeyer flask to the recycling bin.

Part 2: Perform Fine Titrations

Set up the titration as described in steps 1 – 6 in part 1 of experiment 2.

Click and hold the stopcock of the burette to quickly add the before the end point volume of sodium hydroxide determined in the coarse titration.

Add sodium hydroxide in small increments, down to one drop at a time. This can be tedious, but if you click and hold you might miss the exact end point of the titration.

When the solution changes color, stop adding titrant. Record both the pH and volume dispensed.

Clear your station by dragging the Erlenmeyer flask to the recycling bin.

Repeat the fine titration twice more

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