Standardization of NaOH and Percentage Error Report

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

word image 2819 EXPERIMENT 2; PREPARATION OF A STANDARD BASE word image 2820 word image 2821 AND ANALYSIS OF AN UNKNOWN

word image 2822 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).

word image 2823

OH- + C02 HC03′

word image 2824 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) word image 2825
  • Potassium hydrogen phthalate (KHP, KHC8H404, 204.23 g/mol) (—5g per student, word image 2826 to be dried) word image 2827
  • word image 2828 word image 2829 Unknown sample containing potassium hydrogen phthalate (KHP) (—5g per word image 2830 student, to be dried) word image 2831

I. EXPERIMENTAL

word image 2832 A. Preparation of standard and unknown KHP:

  1. Dry —5g of standard potassium hydrogen phthalate (KHP, KHC8H404) at 110 OCTor 1 hr. Cool standard KHP in a desiccator. word image 2833
  2. Dry your entire portion of sample containing an unknown amount ofKHP at 110 oc 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 + 1-120

NqcK 2. Accurately weigh 3 samples (by difference) of dry standard KHP (within word image 2834 10% of the previously calculated value in step I.B.I above) into 3 separate word image 2835 250 mL Erlenmeyer flasks. word image 2836

3. Dissolve each standard word image 2837 o J 927b

word image 2838

KHP

sample

in

50

100

mL

of

deionized

water.

4.

Titrate

with

NaOH

solution

72M

o,

word image 2839 word image 2840 C. Analysis of

word image 2841

I.

word image 2842

needed to require ofNaOH for complete titration,

word image 2843

  1. Accurately wergh samples (by difference) of unknown sample containing word image 2844

KHP (within 10% of the previously calculated value in step l.c. I. above) into word image 2845

word image 2846

ø 3 separate 250 mL Erlenmeyer flasks. word image 2847

word image 2848

  1. word image 2849 Dissolve each unknown sample containing K-HP in 50-100 mL of deionized word image 2850
  2. Titrate with NaOH solution to a phenolphthalein end point. word image 2851

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.

word image 2852 word image 2853 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.

word image 2854

111. RESULTS (These will build up on the Preliminary Results in part Il above)

  1. word image 2855 From your results in I.B (Standardization ofNaOH), calculate the real [NaOH] using each of your standard KHP titration trials. Then, calculate a word image 2856

mean, standard deviation, and 95% confidence interval for the [NaOH].

  1. 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.
  2. word image 2857 Email your instructor with the label of your KHP unknown — she will provide you with the actual wt% KHP in your fitnknown” sample.

word image 2858

 

. D

so

  1. Is your standard [NaOHl accurate and/or precise? How do you know? What could be done differently to improve results?
  2. word image 2859 yourunknown accurate and/or precise? How do you know? What could be done differently to improve results?

word image 2860

word image 2861

0. ICdN) o. 16

1 q 09 €6

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

Order a unique copy of this paper
(550 words)

Approximate price: $22