Chemistry report

Titration Lab Report

Rezan, Manson, Saif, Bryan

Embry- Riddle Aeronautical University

June 10, 2019

Introduction One of the main concepts introduced in the Titration lab is the concept of acidity. According to chemicool.com, acidity can be defined as,”the tendency of a compound to act as a H+ donor.” H+ is a hydrogen ion, which according to the lab module can be thought of as, “a proton floating around in the very polar solvent, water.” According to the Arrhenius Theory, these hydrogen ions are attracted to the oxygen atoms in the water, almost like a magnet, and react to create the hydronium ion H3O+. In other words, acids cause the hydronium concentration in a solution to increase, while a base causes the hydronium concentration to decrease. Because of the inability of this theory to maintain consistent results, the Brønsted-Lowry theory was introduced in 1923. This theory, according to the lab module, states the following, “an acid is a proton donor, any species that donates an H​+ ​ion; an acid must, therefore, contain an ionizable hydrogen in its formula. A base under the new definition is a proton acceptor, any species that accepts an H​+ ​ion; a base must contain a lone pair of electrons to form a covalent coordinate bond with the H​+ ​ion.” The concentration of hydronium ions is measured and recorded in the unit pH. The pH scale is related to the molarity of a solution. Molarity is the number of moles of solute divided by the number of liters of solution. Based on these units, Søren Sørensen introduced the pH scale in 1909. The pH scale ranges from 0-14. Zero to seven can be considered more acidic, while eight to fourteen is more basic. This scale is based on the ability of water to react with itself in an acid-base reaction, which is referred to as the auto- ionization of water. To calculate the concentration of a compound, titrations are often done. ​When performing a titration, a known quantity (called an aliquot) of the unknown sample under investigation is added to a beaker. This sample is called the analyte. Meanwhile, the sample of known concentration, called the titrant, is usually added to a buret​. A pH reader, or a chemical indicator is used to monitor the pH

H –log [H O ] p = 10 3 +

When doing a titration and measuring and recording the pH, the change in pH creates a titration graph with an equivalence point. The equivalence point is the point where the amount of titrant added is enough to completely neutralize the analyte solution. The goal of a titration is to determine at what point, or volume of titrant added the solution is neutralized and changes colors, if using a chemical indicator. Titration will be done by steadily adding 3M HCl acid to a solution of dissolved sodium carbonate and distilled water. We must measure the pH and record at what volume of HCl added, does the solution changes color due to the chemical indicator. Based on the example titration in the lab module, the group expects the solution to change color when apporximately 3 ml of the 3M HCl acid is added to the sodium carbonate solution.

Materials and Methods Material used in this experiment: Glasswares and bottles​: ➸ 50 mL buret ➸ Beakers ➸ Labeled storage bottle ➸ 5mL and 25 mL volumetric pipettes with pump ➸ 100 mL volumetric glass Laboratory devices​: ➸ Vernier LabQuest with pH meter ➸ Balance ➸ stir plate ➸ stir bar Chemicals: ​➸ 6M hydrochloric acid ➸sodium carbonate ➸ 3M hydrochloric acid ➸Methyl orange solution The chemicals used in this experiment has the potential to cause flame and health hazard, irritate skin or eyes, and introduce serious toxicity. Please wear splash goggles, nitrile gloves and lab coats. All waste material should go into waste containers, and must not dump into sink. Label remains of hydrochloric acid with name, pictograms, date, and warning words. The goal is to standardize a sample of hydrochloric acid with a concentration of 3M. As noted, titration is used to determine the concentration of an unknown with very high accuracy.The process allows experimentalists to know the concentration of the solution so it can be used for other purposes.

● Obtain a 6M HCl stock solution and dilute it to 3M in a 100 mL volumetric glass. Rinse a buret with about 5 mL of the diluted solution and make sure the rinse is properly disposed. Fill the buret with the diluted solution and record the starting volume.

● Dissolve about 0.8g sodium carbonate (analyte) with 25-30 mL of water in a 250 mL beaker. Record the mass of sodium carbonate used; it will be used to predict the amount of HCl needed to neutralize it. Add 2-3 drops of methyl orange as the indicator to a beaker.

● Hook the buret to a ring stand, add a stir bar in the beaker, and place it above a stir plate. Connect a pH sensor to LabQuest, suspend it properly, and make sure it’s not hit by the stir bar.

● Drop-by-drop, add 0.2 mL of HCl in progression for first 3.5 mL, record the total amount used in LabQuest (it should be the sum of all previous trials). Add 0.1 mL

until the color changes. Continue adding in 0.2mL increment for 1.0 mL total. Save the data and export it.

● For trial 2 and 3, pH meter is replaced instead of eyes visualization. Repeat point 1 and 2. Be sure to record the starting and ending volume of HCl used.

Figure 1 Summary of experimental procedures for determining the concentration

of an unknown HCl solution.

Figures and Calculations:

Moles HCl (mol):

.086g Na CO .60 0 mol HCl0 2 3 × 1 mol Na CO2 3

105.99 g Na CO2 3 × 1 mol HCl1 mol Na CO2 3 = 7 × 1

−3

Mass HCl (g):

.60 0 mol HCl .277g HCl7 × 1 −3 × 1 mol HCl

36.46 g HCl = 0

Concentration HCl Trial 1 (M):

.33 M HCl0.0057 L HCl 7.60×10 mol HCl−3 = 1

Average Concentration (M):

.45 M HCl3

1.33 M HCl + 1.50 M HCl + 1.51 M HCl = 1

Standard Deviation Concentration HCl (M):

.101 M HCl √ (3−1)(1.33−1.45) + (1.50−1.45) + (1.51−1.45) 2 2 2 = 0

Relative Standard Deviation (%): 00 .98%1.45 M HCl

.101 M HCl × 1 = 6

Percent Error Concentration (M):

00 2.0%3.00 M 1.45 M−3.00 M| | × 1 = 5

Results and Discussion:

Conclusion:

Work Cited:

Chemicool. “Chemistry Dictionary.” ​Definition of Acidity - Chemistry Dictionary​, 2017, www.chemicool.com/definition/acidity.html.