The dependent variables are the salt freezing, and the time it took to freeze. 2. The experiment’s hypothesis is incorrect. The lower the temperature, the less time it took for the water to freeze. Carmen believed that the more salt, the lower the temperature is.
As well as when NaOH is in a solution form it absorbs carbon dioxide from the air which is weakly acidic. When the two mix, it partially neutralizes the solution. So the mass you take one day, will not be the same the next day. Lab 2: Standardizing NaOH Figure 1. This table shows the data collected while standardizing NaOH.
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.
Determination of Molar Mass by Freezing-Point Depression When a solute is dissolved in a solvent, the freezing temperature is lowered in proportion to the number of moles of solute added. This property, known as freezing-point depression, is a colligative property; that is, it depends on the ratio of solute and solvent particles, not on the nature of the substance itself. The equation that shows this relationship is ΔTf = Kf × m× i where ΔTf is the freezing point depression, Kf is the freezing point depression constant for a particular solvent (3.9°C•kg/mol for lauric acid in this experiment1), i is the van’t Hoff factor, and m is the molality of the solution (in mol solute/kg solvent). Since lauric acid is not ionic, its van’t Hoff factor is essentially equal to 1. OBJECTIVES In this experiment, you will • • • • Determine the freezing temperature of the pure solvent, lauric acid.
Name: Patrick Morefield Date: December 06, 2006 Lab Partner: Gabriel Rodriguez Unknown No. : 941 Report Sheet Colligative Properties: Freezing-Point Depression and Molar Mass |1. |Volume of cyclohexane |10..1mL | |2. |Mass of empty insulated test tube and spin bar |345.47g | | |Mass of stir bar, tube and cyclohexane |353.10g | | |Mass of cyclohexane |7.63g | |3. |Mass of insulated test tube, spin bar, cyclohexane and |353.25g | | |unknown | | |4.
Since heated gas is likely to freeze first. When water evaporates the molecule converts heat energy into kinetic energy (energy of motion). Since the hot water evaporates quicker than the cold water, it
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.
pKa of a Weak Acid Introductory Chemistry 1120 pKa of a Weak Acid 1. A results section for the pKa lab. See the example results section from the chemical equilibrium experiment and the details of a results section on page xi of your lab manual. On this table shows the volume of the titration. Unknown acid buret | | | | Trial #1 | Trial #2 | Initial buret reading | 20.5 mL | 21.8 mL | Final buret reading | 40.5 mL | 45.1 mL | Volume of acid added | 20.0 mL | 23.3 mL | This second table shows the calculation of the pH at half equivalence point, average pKa and the average of the unknown acid.
The average density: =0.82+ 0.77+ 0.77 = 2.36 = 2.36/3= 0.79 g/ml Note that the burette was the most accurate in determining accuracy of measured amounts. The average density for all three of these methods is: = 0.76+ 0.73+ 0.79 = 2.28 =2.28/3= 0.76 g/ml Graph Procedure B. Determination of the boiling point of an unknown liquid Note that the atmospheric pressure in the lab room is 100 Kpa. (Xidos, 2013-2014) Required: An assembled boiling point apparatus. Fifteen drops of the unknown liquid was then placed into an empty
(c) Calculate the mass of water formed when 20 g of methane undergoes complete combustion. 6 Deduce the empirical formulae of the following: Moles and empirical formulae 1 Calculate the molar mass of these compounds. (Relative atomic masses H = 1; N = 14; O = 16; Mg = 24; S = 32; Ca = 40; K =39; Cr = 52; Fe = 56.) (a) calcium ethanoate, Ca(CH3CO2)2 (b) chromium sulfate Cr2(SO4)3 (c) magnesium hydroxide, Mg(OH)2 (d) potassium cyanoferrate(III), K3Fe(CN)6 2 When 2.4 g of magnesium