Preparation of a Standard Base and Analysis of an Unknown
Preliminary Results 1:
Molare mass of KHP = 204.23g/mol
Trial # 1:
Amount of KHP = 0.875g
0.875g x x = 0.0043mol of NaOH
Volume of NaOH = 42.8mL x = 0.0428L
[NaOH] = = = 0.1001M
Trial # 2:
Amount of KHP = 0.792g
0.792g x x = 0.0039mol of NaOH
Volume of NaOH = 40.6mL x = 0.0406L
[NaOH] = = = 0.0955M
Trial # 3:
Amount of KHP = 0.820g
0.820g x x = 0.0040mol of NaOH
Volume of NaOH = 39.1mL x = 0.0391L
[NaOH] = = = 0.1027M
Mean of [NaOH] = = 0.0994M
Preliminary Results 2:
Data:
Flask #  Amount of KHP (g)  Volume of NaOH (mL) 
1  1.2864  32.34 
2  1.3119  33.41 
3  1.5801  40.55 
Molar mass of KHP = 204.23g/mol
[NaOH] = 0.09943M
Calculations:
Flask #1:
32.34mL of NaOH x xx x= 0.6565g
WT% = x100% = 51.04%
Flask #  Calculated mass of KHP (g)  WT% 
1  0.6565  51.04 
2  0.6784  51.71 
3  0.8234  52.11 
EXPERIMENT 2; PREPARATION OF A STANDARD BASE AND ANALYSIS OF AN UNKNOWN
Sodium hydroxide,NaOH is a sfrong base commonly used in titrations. However, NaOH solutions also often contain the weak base bicarbonate (HC03) due to reaction with atmospheric carbon dioxide (C02).
OH + C02 HC03′
Therefore, we must determine the real concentration ofNaOH in solution by titration with a primary standard before using the NaOH to titrate an unknown. Primary standards are reagents that are pure and stable enough to be used directly after weighing. In this experiment, we will be using potassium hydrogen phthalate (KHP, KHC8H404) as our primary standard to determine the exact concentration ofNaOH. Then, we will use our standardized NaOH to determine the amount of KHP in an unknown sample.
Chemicals/Reagents and additional materials required:
^{e }—0.1M sodium hydroxide (NaOH) solution (2L per student, same as Exp, l)
 Phenolphthalein indicator solution (l dropper bottle per student)
 Potassium hydrogen phthalate (KHP, KHC8H404, 204.23 g/mol) (—5g per student, to be dried)
 Unknown sample containing potassium hydrogen phthalate (KHP) (—5g per student, to be dried)
I. EXPERIMENTAL
A. Preparation of standard and unknown KHP:
 Dry —5g of standard potassium hydrogen phthalate (KHP, KHC8H404) at 110 ^{O}CTor 1 hr. Cool standard KHP in a desiccator.
 Dry your entire portion of sample containing an unknown amount ofKHP at 110 ^{o}c for 1 hr. Cool unknown KHP sample in a desiccator.
B. Standardization ofNaOH
le The NaOH solution provided is —0.1M. Calculate Of I the M amount according of dried to the
reaction below:
I C H 04 KHC8H404 + NaOH KNaC8H404 + 1120
NqcK 2. Accurately weigh 3 samples (by difference) of dry standard KHP (within 10% of the previously calculated value in step I.B.I above) into 3 separate 250 mL Erlenmeyer flasks.
3. Dissolve each standard o J 927b
KHP
sample
in
50
100
mL
of
deionized
water.
4.
Titrate
with
NaOH
solution
72M
o,
C. Analysis of
I.
needed to require ofNaOH for complete titration,
 Accurately wergh samples (by difference) of unknown sample containing
KHP (within 10% of the previously calculated value in step l.c. I. above) into
ø 3 separate 250 mL Erlenmeyer flasks.
 Dissolve each unknown sample containing KHP in 50100 mL of deionized
 Titrate with NaOH solution to a phenolphthalein end point.
Il. PRELIMINARY RESULTS
1. From your results in I.B (Standardization ofNaOH), calculate the real [NaOHl using each of your standard KHP titration trials. Then, calculate a mean [NaOHl.
2. From your results in l.c (Analysis ofan Unknown containing KHP), calculate the weight percent of KHP in your unknown sample usmg each of your unknown KHP titration trials. Then, calculate a mean wt% KHP.
111. RESULTS (These will build up on the Preliminary Results in part Il above)
 From your results in I.B (Standardization ofNaOH), calculate the real [NaOH] using each of your standard KHP titration trials. Then, calculate a
mean, standard deviation, and 95% confidence interval for the [NaOH].
 From your results in l.c (Analysis ofan Unknown containing KHP), calculate the weight percent ofKHP in your unknown sample using each of your unknown KHP titration trials. Then, calculate a mean, standard deviation, and 95% confidence interval for the wt% KHP.
 Email your instructor with the label of your KHP unknown — she will provide you with the actual wt% KHP in your fitnknown” sample.

 Is your standard [NaOHl accurate and/or precise? How do you know? What could be done differently to improve results?
 yourunknown accurate and/or precise? How do you know? What could be done differently to improve results?
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Preparation of a Standard Base and Analysis of an Unknown
Preliminary Results:
Data:
Flask #  Amount of KHP (g)  Volume of NaOH (mL) 
1  1.2864  32.34 
2  1.3119  33.41 
3  1.5801  40.55 
Molar mass of KHP = 204.23g/mol
[NaOH] = 0.09943M
Calculations:
Flask #1:
32.34mL of NaOH x xx x= 0.6565g
WT% = x100% = 51.04%
Flask #  Calculated mass of KHP (g)  WT% 
1  0.6565  51.04 
2  0.6784  51.71 
3  0.8234  52.11 