SCH3U Name: Farhan

Louise Arbour Secondary SchooL

SCIENCE DEPARTMENT
T/I C
GRADE 11 UNIVERSITY CHEMISTRY

CHEMICAL QUANTITIES: TITRATION ANALYSIS OF H2SO4 (VIRTUAL)

Purpose: To find the concentration of H2SO4 in a sample.

Balanced Chemical Equation: [C]

Materials: [C]
● Burette
● Flask
● Indicator
● NaOH
● H2SO4
● Phenolphthalein
● bromthymol blue

Introduction: Adding a drop of strong acid or base into a neutralized solution is similar to
adding a drop of strong acid or base to water—it causes an abrupt change in pH. By
using an appropriate indicator, a chemist can tell when a solution is neutralized by
monitoring its color.

Procedure:
Step 1: Go to https://www.explorelearning.com
Step 2: Click on the “Enroll in a Class” button in the upper right hand corner of the web
page.
Step 3: Type in your class code: V9GMF8

Step 4: Click “Continue” and follow the directions on the site to complete your
enrollment.

Get the Gizmo ready:

● Click Reset.
 ● Select 1.00 M NaOH for the Burette and Mystery H2SO4 for the Flask.

Observe:
1. Select Phenolphthalein for the Indicator. Look at the flask. What is the color of the
phenolphthalein indicator? _____Colorless_____________

2. What does this tell you about the pH of the solution in the flask? ____The pH level
is below 8.2.__________________
Solutions with a pH below 7.0 are acidic, while those with a pH above 7.0 are
basic.

Measure:
A titration can be used to determine the concentration of an acid or base by
measuring the amount of a solution with a known concentration, called the titrant,
which reacts completely with a solution of unknown concentration, called the analyte.
The point at which this occurs is called the equivalence point.

3. Carefully add NaOH into the flask until the phenolphthalein begins to change its
color. Stop adding NaOH when the color change is permanent. How much
NaOH was required to cause the indicator to change color? Record your
observations in column labelled Trial #1 in the table below. Repeat this process
and record your observations under Trial #2.

4. Click Reset and change the indicator to bromthymol blue. Carefully add NaOH
into the flask until bromthymol blue begins to change its colour. Stop adding
NaOH when the colour change is permanent. How much NaOH was required to
cause the indicator to change color? Record your observations in column
labelled Trial #3 in the table below. Repeat this process and record your
observations under Trial #4.

Observations: (Make sure to include units in your chart!) [C]

Trial #1 Trial #2 Trial #3 Trial #4

Volume of H2SO4 100 ml 100 ml 100 ml 100 ml
used

Volume of NaOH
used 21.7 ml 21.7 ml 21.6 ml 21.6 ml
Calculations: [T/I]

Average volume of (21.7 ml+21.7 ml+21.6 ml+21.6ml)/4

NaOH used 21.65 ml or 2.165*10^-2L

nNaOH= C*V
Number of moles of
NaOH
nNaOH= (2.165*10^-2(1.00M)
=0.02165 mol

nH2SO4= nNAOH=need/have
=(0.02165 mol= ½
Number of moles of
nH2SO4= 0.0108
H2SO4

M=Mol/L
Concentration of
=0.0108/0.1
H2SO4 (Experimental Value)
M=0.108 mol/L or 0.108 M

Analysis:

1. Calculate the experimental value of the H2SO4 concentration. Show all steps
of your calculations. [T/I]

M=n/V
=0.0108 mol H2SO4/0.1 L
M=0.108 mol/L or 0.108 M of H2SO4
 2. Calculate the % error between the expected concentration and your
measured concentration (experimental value). [T/I]

% Error = |expected concentration - measured concentration | x

100%
                                expected concentration                      

% Error=(0.125 M-0.108 M/0.125)x100%

=15.7% error

3. Determine the %(m/v) concentration of the sulfuric acid. [T/I]

MH2SO4=2(1.01)+(32.07)+4(16.00)=98.09g/mol

m=nM
=(0.0108 mol(98.90 g/mol)
m= 1.07 g

Percent= (mass/volume)*100
=(1.07g/100ml)*100
=1.07%

Discussion:

1. Discuss errors (at least two) that may have occurred in your lab
procedure and suggest ways in which those errors could be minimized
in the future. (DO NOT INCLUDE HUMAN ERRORS) [T/I]
 Two experimental errors that may have occurred during this lab was
the overall digital aspect of it.For starters I couldn’t control the flow of the mystery
H2SO4 and I was limited to 2 flows in which I went back and forth changing the overall
flow of the solution. This can be resolved if there was only one option as to how the
H2SO4 solution flowed rather than two making it a much fairer test.Instead of a pouring
lever, this issue could be avoided by using a button that allows for quick on and off flow
rather than a flow change. Second, even if it was a digital lab, there was no control
over the overall temperature, which would have influenced the lab's accuracy
because we don't know if mixing a warmer solution with a lower temperature solution
would have affected the pH level and overall result. There should be a parameter to
modify the temperature of the solutions to fix this mistake.

2. A titration curve is a graph of pH vs.

volume of titrant. The graph at right
shows a typical titration curve for
the titration of a strong acid by a
strong base. (A strong base is one
that has relatively high dissociation
in water.) Why do you think the
titration curve has the shape it has?
How would you expect the titration
curve to look for the neutralization
reaction of H2SO4 with NaOH? [T/I]

The pace at which the pH increases is exceedingly slow until a specific amount
of base is introduced, as can be seen from the graph of pH versus titrant volume.
The pH will be low since the Erlenmeyer flask only holds 100 mL of sulfuric acid. As
a result, even though the equivalence point increases dramatically, a base
continues to be created and the base keeps building up until that point, as
shown in the graph. A gradual increase in pH, which is directly related to the
acid becoming more basic, causes the graph to gradually grow in ph. The
reason for the dramatic increase in pH at the equivalency point is due to a
chemical reaction that occurs there. Because we know that a neutral pH is 7, this
graph shows that the neutralisation reaction begins when the pH reaches 7. As a
result, all of the basic solution that was previously added began to react when
the volume reached 7. Everything beyond the equivalency point represents the
base conquering the acidity in the substance, and it is increasing ever so slightly
because the neutralising reaction had already occurred, and there is no
reaction to occur now that it is a base. The neutralisation reaction of H2SO4 with
NaOH, as well as the acid, HASO, would be appropriately represented by this
graph. At a pH of 7, it is also neutralised. Although this graph begins with a pH of
 2 for our acid, H2SO4 would begin with a pH of 0.666 because that is our acid's
initial pH. Aside from that, the graph's trend would remain unchanged.

3. Once you know the concentration of a strong acid or a strong base,

you can estimate its pH. Calculate the pH of the Mystery H2SO4 based
on the concentrations you determined. Show all your work. [T/I]

H2SO4 (aq) 2H+ (aq) + SO4^2-(aq)

[H+] = 2 [H2SO4) = 2[0.108 M) = 0.216 M
pH = -log[H3O+] = -log(0.216) = 0.666

4. Why is it necessary to rinse the burette with a few millimeters of the

sodium hydroxide solution used in the titration before filling it up with
this solution? [C]

Because the burette is used with a variety of chemical solutions in various titrations, it is
important to rinse it with sodium hydroxide. We can't tell whether the burette was
previously filled with a solution other than sodium hydroxide based on this. If this is the
case, the other substance's initial pH will differ from that of sodium hydroxide, resulting in
a titration error in our entire lab. Furthermore, we are unsure if a burette has been
cleaned with water before use; if so, and not thoroughly dried, water would induce
dilution, which will result in an error in the lab.

Conclusion: Summarize your quantitative results. [C]

 To summarise, using a concentration of 1.00 M sodium hydroxide solution, I was
able to titrate 100 mL of sulfuric acid (H2SO4) with a concentration of 0.108 M, a
pH of 0.666, and a 1.07 percent percent composition (NaOH). I did four tests, two
with a phenolphthalein indicator and two with a bromothymol blue indicator, for
a total of 21.65 ml base/NaOH, to achieve these findings. When comparing my
forecasts for sulfuric acid concentration to the actual readings, I had a 15.7
percent inaccuracy. I expected a concentration of 0.125 sulfuric acid to be
produced, but instead received a concentration of 0.108 M.

SCH3U0 Titration Analysis of H2SO4 Report Rubric and Checkbric

Achievement Criteria
Chart
Category
Communicatio • Provides detailed titles and chart numbers for charts and graphs.
n
• Provides detailed answers to discussion questions using full sentences. Refers to
Overall Level: quantitative and qualitative results to support discussion answers.

• Provides a final conclusion summarizing qualitative and quantitative results.

__________
Inquiry Observations:
• Records detailed qualitative observations including mention of state, colour,
clarity and observable changes during reactions.
Overall Level:
• Records accurate quantitative results including units and appropriate precision.

Analysis and Discussion:

_________ • Provides accurate and detailed calculations and graphs including formulas,
units and appropriate steps.

• Provides thoughtful answers to discussion and analysis questions.

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