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Results And Discussion

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Chemistry
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Wilkes University
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Results
Table 1. Standardization of NaOH solution.
Trial 1
Trial 2
Trial 3
mass of KHP, g
0.8668
0.7680
0.5947
volume of NaOH used, mL
40.91
36.05
28.80
molarity, M
0.1037
0.1043
0.1011
mean molarity, M
0.1031
standard deviation
0.0017
95% confidence interval for [NaOH]
0.0988 M 0.1073 M
Table 2. Analysis of unknown containing KHP.
Trial 1
Trial 2
Trial 3
volume of NaOH used, mL
39.50
36.13
37.61
number of moles of KHP, mol
0.004098
0.003769
0.003803
mass of KHP, g
0.8369
0.7697
0.7766
mass of sample, g
2.4193
2.3664
2.4829
weight % (w/w) KHP
34.59
32.53
31.28
mean weight % KHP
standard deviation
95% confidence interval for weight %
Discussion
The first part of the experiment was to standardize the NaOH solution. The concentration of NaOH
solution was determined by titrating a solution containing a known amount of KHP. The number of moles
of KHP that reacted is proportional to the number of moles of NaOH. The chemical equation that shows
the process is given as follows
KHC
8
H
4
O
4
+ NaOH → KNaC
8
H
4
O
4
+ H
2
O
The mean molarity from the three trials was 0.1031 M with a standard deviation of 0.0017. The three
trials were accurate since all of these gave concentration values close to 0.1 M and the standard deviation
suggests that the values are also precise since the value of the standard deviation is low. This means that
the values are near to each other. Possible sources of error are (1) not all of the KHP was dissolved in the
solution, leading to low NaOH concentration, and (2) some of the NaOH was trapped in the stopcock,
therefore the number of moles of NaOH reacted is lower than expected, leading to higher calculated
concentration.
After the standardization of the NaOH solution, the amount of KHP in an unknown solution was also
determined. From the three trials, a mean weight percent of 32.80% KHP with a standard deviation of
1.67 was determined to be present in the unknown sample. At 95% confidence, the determined interval
wherein the true value lies is 28.64% 36.96%. The actual percentage of KHP in the sample was 33.70%.
This value is within the calculated 95% confidence interval. Thus, the obtained value agrees with the
actual value. The percentage from the three trails was accurate since they were all close to the actual value.
Also, the values were precise since they are close to one another as shown by the value of the standard
deviation. One of the possible errors in this part of the experiment is that not all of the KHP in the sample
reacted with NaOH. To address this, ensure that the solution is properly dissolved and include enough
amount of indicators to clearly show the endpoint of the reaction.

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To conclude, the molarity of the NaOH solution was 0.1031 M while the weight percent of KHP in the
unknown sample was 32.80%. Both these values were accurate and precise as shown by the statistical
data presented. To further improve the results, ensure that the KHP in samples are all dissolved and the
endpoint of the titration should be properly determined to ensure that the data are as accurate as possible.
Supplemental Information
A. Standardization of NaOH solution
Trial 1:
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
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
Trial 2:

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


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
Trial 3:


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


Mean Molarity:

    

Standard Deviation of Molarity:

  
  
  
  

95% Confidence Interval:
 




 





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Results Table 1. Standardization of NaOH solution. Trial 1 0.8668 40.91 0.1037 Trial 2 0.7680 36.05 0.1043 0.1031 0.0017 0.0988 M – 0.1073 M Trial 3 0.5947 28.80 0.1011 Trial 1 39.50 0.004098 0.8369 2.4193 34.59 Trial 2 36.13 0.003769 0.7697 2.3664 32.53 32.80 1.67 28.64% – 36.96% Trial 3 37.61 0.003803 0.7766 2.4829 31.28 mass of KHP, g volume of NaOH used, mL molarity, M mean molarity, M standard deviation 95% confidence interval for [NaOH] Table 2. Analysis of unknown containing KHP. volume of NaOH used, mL number of moles of KHP, mol mass of KHP, g mass of sample, g weight % (w/w) KHP mean weight % KHP standard deviation 95% confidence interval for weight % Discussion The first part of the experiment was to standardize the NaOH solution. The concentration of NaOH solution was determined by titrating a solution containing a known amount of KHP. The number of moles of KHP that reacted is proportional to the number of moles of NaOH. The chemical equation that shows the process is given as follows KHC8H4O4 + NaOH → KNaC8H4O4 + H2O The mean molarity from the three trials was 0.1031 M with a standard deviation of 0.0017. The three trials were accurate since all of these ...
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