Experiment #2 report form instructions

Download the *.pdf form from the lab website and open it using Adobe 7.x or newer (we strongly recommend you update to the latest version available by going to the Adobe website). Fill in and print the form using Adobe Reader or Adobe Acrobat. If you are unsure what to put in a field, hover your cursor over the field and read the tooltip.

Do not attach any additional pages. Everything you need to fill in is contained in this form. Refer to the appendices in your lab manual for instructions on how to properly complete the sections in this report form. The only section in which you should hand write is the Sample Calculations section.

Other instructions for specific sections:

Introduction: balance the provided equations using the drop-down menus provided.

Procedure: appropriately reference the procedure as detailed in your lab manual.

Data: fill in the provided tables with your in-lab and calculated values, and set appropriate units for the values using the drop-down menus provided.

Sample calculations: provide a sample set of calculations for a single titration from both parts of the experiment (i.e. one titration for the standardization and one titration for the determination). Refer to the appendix for instructions on how to properly present equations. Only show the calculation for a single titration in each section (although you will have to apply the same calculation to your other titrations in order to fill in the data tables; a spreadsheet program like Microsoft Excel is well suited to apply the same calculation to multiple values). Due to the limitations of pdf forms, there is no option to insert digital equations. Write out your calculations by hand in the spaces provided after printing. All of the calculations you will need to perform are mentioned in this report form.

Discussion: fill in the discussion with your values and select the appropriate item from the drop-down menu where applicable. Complete the sentences to discuss the precision of your titrations (if a %RSD lower than 5% is considered good, what does that indicate about your titrations).

References: properly cite the appropriate references for this report form as detailed in your lab manual.

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Time to drop the base!

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Experiment #2: Time to drop the base!

Introduction

Quantitative determination of the concentration of a specific chemical is a core technique in chemistry. Although there are many different instruments which can perform these determinations, this can also be done by exploiting simple reactions and titrations. One example of a simple, commercially available medication is antacid tablets, which are used to treat acid-reflux. In this experiment, a series of titrations were performed to determine the amount of antacid (in this case CaCO3) in a commercially available tablet. In order to accurately determine the amount of CaCO3, it was first neutralized by a known excess of acid (equation 1), and the remaining acid was back-titrated with a standardized solution of base (equation 2). To determine the endpoints of the titration reactions, two indicators were used: phenolphthalein and bromophenol blue.

Reaction for the neutralization of calcium carbonate and hydrogen chloride

CaCO3 + HCl CaCl2 + CO2 + H2O (1)

Reaction for the neutralization of sodium hydroxide and hydrogen chloride

HCl + NaOH H2O + NaCl (2)

Procedure1

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Data

Table 1: reagents used.

Reagent MW ( ) Amount used Moles used

( )

Table 2: titration data for the standardization of the sodium hydroxide solution.

Titration #

Volume ( ) Number of moles NaOH

( )

Concentration of NaOH

( ) Initial Final Added

Average Standard Deviation

%RSD

Table 3: titration data for the analysis of antacid.

Titration #

Volume ( ) Number of moles NaOH ( )

Number of moles HCl ( )

Initial Final Added In this titration

Neutralized by NaOH

Neutralized by antacid

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Table 4: determined amount of calcium carbonate in the antacid tablet.

Titration #

Number of moles CaCO3 neutralized ( )

Number of moles CaCO3 in entire tablet ( )

Mass of CaCO3 in entire tablet

( )

Average Standard deviation

%RSD

Sample Calculations

Example set of calculations for the standardization of sodium hydroxide solution (values are from titration # )

Number of moles of potassium acid phthalate

Volume of sodium hydroxide solution added

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Number of moles of sodium hydroxide

Concentration of sodium hydroxide

Average concentration of sodium hydroxide

Standard deviation of sodium hydroxide concentration

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Percent relative standard deviation of sodium hydroxide concentration

Example set of calculations for the antacid determination (values are from titration # )

(1) Volume of sodium hydroxide added

(1) Number of moles of sodium hydroxide added

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(2) Number of moles of hydrogen chloride neutralized by sodium hydroxide

(3) Number of moles of hydrogen chloride in this titration aliquot (before neutralization by antacid or base)

(4) Number of moles of hydrogen chloride neutralized by calcium carbonate

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(4) Number of moles of calcium carbonate neutralized by hydrogen chloride

(5) Number of moles of calcium carbonate in entire tablet

(6) Mass of calcium carbonate in entire tablet

(6) Average determined calcium carbonate in entire tablet

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(6) Standard deviation of average calcium carbonate mass in entire tablet

(6) Percent relative standard deviation of average calcium carbonate mass in entire tablet

(7) Comparison of determined mass of calcium carbonate in entire tablet to advertised amount of calcium carbonate 2

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Discussion

In the standardization titrations for the sodium hydroxide solution, the titrations were performed. The average concentration of the sodium hydroxide solution was found to be with a standard deviation of (Table ). The relative standard deviation of suggests that:

The titrations for determining the amount of antacid in the tablet were performed. The average amount of CaCO3 in the supplied tablet was with a standard deviation of (Table ). The relative standard deviation of suggests that the replicate titrations were:

When compared to the advertised CaCO3 amount in each tablet ( ),3 the determined value of is different.2 Based on this comparison, the company supplying these tablets is advertising the amount of CaCO3 in their tablets.

References