Spreadsheet Assignment #2: Titration of Unknown Acid Report
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During routine laboratory titrations, the normality of the titrant changes from time-to-time. Because of this,
it is helpful to have a spreadsheet that is formatted to calculate results of
titrations based upon a variable cell that contains the current normality of
the titrant used in a titration. Construct a
spreadsheet that contains a cell for sodium hydroxide normality. Use the
value in this cell to calculate unknown acid normalities
from titration volumes given below. Be sure to include a date for the
last normalization of the sodium hydroxide titrant
and a space for your name, sample identification and so forth. (Note:
Normality is defined as equivalents (moles) of H+ or moles of
Unknown Acid Titration Report
Sample Set 1:
NaOH
Normality: 0.1158 equivalents/Liter
Date
Normalized: Sept. 9
|
Sample ID |
Rep# |
Unknown Acid Volume
(mL) |
NaOH
Volume (mL) |
Calculated
Normality of Unknown Acid (equiv./ Liter) |
Average of 3 Replicates: |
Standard Deviation of 3 Reps. |
RSD(%) |
|
M-321-A |
1 |
10.00 |
36.89 |
|
|
|
|
|
|
2 |
10.00 |
36.94 |
|
|||
|
|
3 |
10.00 |
36.75 |
|
|||
|
M-321-B |
1 |
25.00 |
46.02 |
|
|
|
|
|
|
2 |
25.00 |
46.18 |
|
|||
|
|
3 |
25.00 |
45.88 |
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|||
|
M-321-C |
1 |
10.00 |
28.00 |
|
|
|
|
|
|
2 |
10.00 |
28.08 |
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|||
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|
3 |
10.00 |
28.12 |
|
After
completing this table including formulas and results, print a copy. Then, for the second set of titrations, you
can simply input the new data for Sample Set 2, without having to reenter all
the formulas.
Alternatively,
you may copy this table by selecting (highlighting) the cells in the table and
then clicking on Edit > Copy. Move to
a blank area of the spreadsheet (e.g., below the existing table) and past a
copy of the table into the new region by clicking Edit > Paste Special. Enter the NaOH
normality in the new cell and the date it was normalized. Edit the formulas in the calculations column
to reference the new cell containing the NaOH
normality. Enter the new data for Sample
Set 2 and calculated the Normality of each sample and their averages. Print a report for Sample Set 2. Submit both printed tables as your results
for this exercise.
Sample Set 2:
NaOH
Normality: 0.1301 equivalents/Liter
Date
Normalized: Sept. 22
|
Sample ID |
Rep# |
Unknown Acid Volume
(mL) |
NaOH
Volume (mL) |
Calculated
Normality of Unknown Acid (equiv./ Liter) |
Average of 3 Replicates: |
Standard Deviation |
RSD (%) |
|
X-89-D |
1 |
20.00 |
15.78 |
|
|
|
|
|
|
2 |
20.00 |
16.02 |
|
|||
|
|
3 |
20.00 |
15.94 |
|
|||
|
X-89-E |
1 |
10.00 |
36.64 |
|
|
|
|
|
|
2 |
10.00 |
36.50 |
|
|||
|
|
3 |
10.00 |
36.60 |
|
Analyst: ___________________________________ Date: ______________
Programming Tips:
|
Excel command: |
Result |
|
F4 (function key) |
Locks a referenced cell in a formula. This puts a dollar sign in front of the letter and/or number of the cell address (e.g., $B$4). When copied to another location, the dollar signs prevent relative movements of the pointers as the formula is copied across or down a series of columns or rows. Note: Pressing the F4 key repeatedly places the dollar signs in different positions (e.g., $B4 or B$4 or removing them completely). |
|
|
|
Writing a formula for each cell would be very tedious and time consuming. When a cell containing a formula is copied across a range of cells, all the cells referenced in that formula shift in the corresponding direction. To prevent this, cells that are referenced in a formula can be locked. A reference can be locked by putting dollar sign ($) in front of its column and row references, such as: $B4, B$4, and $B$4. $B4 locks the Column, B$4 locks the Row, and $B$4 locks both.
When writing or editing formulas you can use the F4 Function key to toggle all 4 possible locking combinations (including none) for the referenced cell closest to the cursor. Be sure to sign your report and include the spreadsheet number on your printout (Spreadsheet #2).
Note:
It is possible to write only two equations for this entire assignment, a single
formula for each section, by using locked reference cells and then copying the
formulas across the range. Try to
complete this spreadsheet by utilizing the copy and paste functions as much as
possible.
Chemistry/Calculation Tips:
Recall that for the titration of a monoprotic acid with sodium hydroxide, you may use a simple equation to calculate the results:
(Cacid) x (Vacid)
= (Cbase) x (Vbase),
where C is concentration (usually in units of Molarity or Normality) and V is volume (usually in mL). Rearranging this equation allows calculation of a fourth unknown value from the other three values.