In the first part, five 100 mL flasks of 5 mL ligand solution, 5 mL 2 M sodium acetate, 4 mL 3 M NH2OH, and 1-5 mL Fe2+ solution are diluted with water. The absorption spectrum for varying concentrations of Fe2+ are measured using a spectrophotometer and the data is graphed in Excel. The slope of the line is ε in the Beer-Lambart equation A = εcl. In the second part of the experiment, eleven flasks containing diluted stock solutions of Fe2+ and ligand are mixed with 5 mL 2 M sodium acetate and 4 mL 3 M NH2OH and diluted with water. The absorption spectrum is measured using a spectrophotometer and the data is graphed in Excel.
Chromatography: Separating Mixtures Introduction: Magic marker inks are often mixtures of several compounds. Paper chromatography is a common method of separating various components of a mixture. After separation, you can observe the different colors that make up a particular color of magic marker ink. You can also calculate a ratio Rf, which compares how far each compound traveled to how far each solvent (substance that dissolves another substance) traveled during the experiment. Rf = Ds/Df Ds = Distance traveled by the compound Df = Distance traveled by the solvent Materials: coffee filter, tape, rubbing alcohol, water, 3 different color magic markers (not permanent); 3 identical tall, narrow drinking glasses; metric ruler, 3 pencils Pre-lab Questions: 1.
Rf = Ds/Df Ds = Distance traveled by the compound Df = Distance traveled by the solvent Materials: coffee filter, tape, isopropyl alcohol (rubbing alcohol), water, 3 different color magic markers (not permanent); 3 identical tall, narrow drinking glasses; metric ruler, 3 pencils Pre-lab Questions: List one extensive and one intensive property of marker ink. Intensive - color Extensive - volume Define mixture. a substance made by mixing other substances together. Is tap water a heterogeneous or homogenous mixture? Explain your answer.
Observations of Physical and Chemical Changes Purpose- The different tests can interact and change in different ways, by doing these tests we can figure out if it could be either a physical change or chemical change by observing the test and chemicals. Procedure- In test one, you mixed a small amount of iodine in each test tube and fill one of the with just tap water and the second one with hexane. Test two, you measure 5 grams of barium hydroxide and same measurement of ammonium chloride and stir with a stirring rod. Test three, you use a small piece of steel wool and you place it over a Bunsen burner using tongs and observe what you see. Test four, by using a plastic bag, you place a spoon full of calcium chloride in one corner and
How do you go from calculated/measured values to accomplishing stated purpose? (4 pts) The purpose of this lab is to determine the exact concentration of an unknown acetic acid solution. Titrations for two different reactions will be performed. Controlled volumes of one reagent are added to a flask containing the other reagent until the equivalence point of the reaction is reached, one between sodium hydroxide (NaOH) and potassium hydrogen phthalate (KHP) and the other between NaOH and acetic acid (CH3COOH). NaOH (aq) + KHP (aq) —› Na+ (aq) + K + (aq) + P2- (aq) + H2O (l) NaOH (aq) + CH3COOH (aq) —› Na+ (aq) + CH3COO- (aq) + H2O (l) The titration of NaOH with KHP will identify the concentration of the NaOH provided.
-Use the titrations of the following chemical reactions: NaHCO3 + HCl (aq) NaCl (aq) + H2O (l) + CO2 (g) 2HCl (aq) + Na2CO3 (s) 2NaCl (aq) + H2O (l) + CO2 (g) Experimental procedure- Two Erlenmeyer flask must be labeled “unknown 1 and unknown 2”. Assure that all containers used are dried and cleaned properly. Two bigger flask are labeled “waste” according to each unknown. A pipette is set up and primed with HCl. The two unknown solids are weighed to a mass of 0.15g each.
Hydrate Lab The purpose of this lab is to analyze the percent water in a crystalline hydrate and to indentify the hydrate from a list of possible unknowns. The solid hydrate will be heated to remove the water, and the percent can be found by measuring the mass of the solid before and after heating. The hydrate will be indentified by comparing the percent water in the hydrate with the percent water calculated for the possible unknown. Before the lab there are pre-lab questions: 1. Describe the three general safety rules for working with a Bunsen burner.
CHEMISTRY September 25, 2010 Experiment #5: Percentage of water in a Hydrate Summary of Principles In this lab, students will calculate the amount of water in an unknown hydrate. A hydrate is a compound with a specific number of water molecules associated with the ions of that compound. A hydrate may form when an anhydrous compound is exposed to atmospheric water or when the ionic compound is crystallized from an aqueous solution. An anhydrous compound is a substance without water. There are two parts to this lab.
These tests consisted of a wafting test, a solubility test in deionized water, and a pH test. The unknown’s characteristics, discovered through the physical tests, were then compared with known cations: Sodium, Potassium, Calcium, Ammonia, and Magnesium. Flame tests were performed in order to classify the unknown cation. A small amount of the solid unknown ionic compound was placed on a watch glass. A wet swab was used to collect a small sample of the compound.
What is the identity of your unknown? Justify your conclusion by comparing the observed molecular weight and pKa values to those for all amino acids that might have been your unknown. B) Examining the effect of ionic strength on the pKa of a weak acid. Restandardize the pH meter with both pH 4 and pH 7 buffers. Why is this necessary?