Lab 1: Determining Molar Mass by Freezing Point Depression Xiaoyu Shi Partha P Samadder CHEM 152IN(CRN:12570) September 14, 2014 * Introduction: In this experiment, we are going to measure the freezing point depression of an aqueous solution of an unknown organic compound. Determine the molar mass of the unknown compound from the freezing point depression data. We also will practice the formula applied to freezing point depression, the molality and the molarity. We will use ice-salt water and a thermometer to determine the freezing point of the unknown organic compound. Then we can use the formula to find the molar mass of the unknown organic compound.
Identify some specific changes that you would suggest for Carmen’s experiment in order to specifically test her hypothesis. Give a specific explanation for why these changes are improvements. ANSWERS: 1. The independent variables in Carmen’s experiment are the amount of salt added, and the amount of time Carmen lets the salt sit. The dependent variables are the salt freezing, and the time it took to freeze.
Chapter Two: Freezing Point Depression Measurements Purpose: The purpose of this lab is to measure freezing points and freezing point depression for several solutions. The freezing point depression constant (Kf) for p-xylene was calculated from freezing point measurements and used to estimate the molar masses of three unknown solutes in a p-xylene solution. The end goal of this lab experiment is to correctly identify these three unknown solutes. The molar mass of a solute is able to be determined through freezing point depression measurements because the increase in solutes disrupts crystal formation, requiring a lower temperature to form a lattice. This colligative property is important in many industries, but is clear to see when using ordinary salt to remove ice from steps or a driveway.
Sodium Hydroxide + Hydrochloric Acid Sodium Chloride + Water NaOH(aq) + HClaq → NaCl(aq) + H2O(l) Variables Independent The independent variable of the experiment was the amount of sodium hydroxide that we added to the acid. To keep the variable controlled we would measure 1 ml of the sodium hydroxide and pouring that to the hydrochloric acid. Dependent The dependent variables of the experiment were the temperature and the pH number of the mixture. To control the pH and temperature use the electronic probe and data logger. Controlled The controlled variables of the experiment were: A.
I inserted the digital thermometer into the test tube and took reading every 30 seconds until the readings remained constant. The readings for the distilled water did not change. I then placed the test tube in the beaker’s ice water bath and set the stopwatch at zero. I carefully stirred the water in the test tube with the thermometer and recorded the temperature of the water at 30-second intervals. Data Table 1: Pure Water Time in seconds | Distilled H2O Room Temp | Distilled H2O Ice bath | 0 | 2431o C | 24.3o C | 30 | | 4.8o C | 60 | | 0.7o C | 90 | | -0.4o C | 120 | | -0.8o C | 150 | | -.10o C | 180 | | -.10o C | Data Table 2: Salt Solution Time in seconds | Salt Water Room Temp | Saltwater Ice Bath | 0 | 20.8O C | 14.2o C | 30 | | 3.0o C | 60 | | 0.2o C | 90 | | -0.3o C |
Introduction The purpose of this lab is to determine the normality of an unknown base using a volumetric titration. The volumetric titration used for this experiment consisted of a standard acid called potassium hydrogen phthalate (KHC8H4O4) titrated with a weak unknown base. An acid-base indicator called phenolphthalein is used in order to view the reaction proceeding to completion. The indicator allows visualization of the acid changing colour when the solution has reached the end point. The normality of the unknown base is calculated after the solution has reached the end point.
Terrall Brooks Organic Chemistry 203 Monday 12:50 pm -4:50 pm Dr. Shaw Fractional Distillation Abstract Distillation is the process of converting a liquid to a vapor, condensing the vapor, and then, collecting the distillate in another container. There are two types of distillation namely, simple and fractional. My group was assigned to perform fractional distillation which aims to separate the components in a liquid mixture having different boiling points. We had to record the temperature and volume collected at 1-mL intervals to compute and determine the unknown mixture we used in the process. The results were Acetone which boiled at 56 degrees and Toluene which boiled at 111 degrees.
Abstract In this experiment a sample of liquid substance is evaporated in order to measure certain physical properties of the substance as it is condensed. The molar mass of the unknown liquid is determined when the gas laws are used to calculate the number of moles. Materials Chemical List: 1. Aluminum Foil a. Chemical Formula: 4AL(s) + 3O2(g) → 2Al2O3(s) b. Melting Point: 1218˚F, 659˚C c. Amount Needed: One piece, big enough to cover the top of a small test tube 2.
* Solid- * A form of matter that is of definite shape and volume. * Liquid- * A form of matter that is variable in shape but definite in volume. * Celsius (oC)- * A scale of measurement for temperature that registers the freezing point of water at 0o and the boiling point of water at 100o. * Background- * The basic point of this lab was to find at what temperature would the Lauric Acid melt. Now to find this we would also have to look at the heating curve of the experiment.
By recording the amount of silver nitrate (AgNO3) is used, the amount of the chloride used is figured. An indicator is used to help determine when the reaction is complete. The indicator used in this experiment is potassium chromate (K2CrO4). The recorded volume of silver nitrate (AgNO3) used is then used to determine the molarity of the silver chloride (AgCl) created. Moles of AgCl = (Volume of AgNO3 added) × (Molarity of AgNO3) Using the molarity of the silver chloride (AgCl) and the atomic weight of the chloride (35.4527), the weight of the chloride from the original unknown chloride salt sample.