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Question: i need help for answering background conclusion questions and critical...

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I need help for answering background, conclusion questions and critical thinking, also I need help how to find the molar mass of the unknown in table 4 and van hoff factor in table 2
COLLIGATİVE PROPERTİES: FREEZING POINT DEPRESSION Belore you come to the lab you need to print and read the experiment manual Also, draw all tables in your notebook Suy aligative property of a soution by determining the freezing point depression of dilferent squeous i) Determine the molecular weight of the unknown organic solutions Determine if a solute is an electrolyte or non-electrolyte INTRODUCTION Solutions are homogeneous mixtures that contain two or more substances. The major component is called the solvent and the minor component(s) are called the solute(s). Since the solution is primarily composed of solvent, the physical properties of the solution resemble those of the pure solvent However, some of these physical properties caliled coligative properties, are independent of the nature of the solute and depend only upon the concentration of solute partcles. Éxamples of colligative properties include vapor pressure reduction, boiling point elevation, freezing point depression, and osmotic pressure Pure water freezes at 00°C(273 K). bois at 100 О-С (373 K. and exerts a vapor pressure of 23.S mm HS at SOC (298 K). These values are altered by the presence of a solute. You are probably familiar with some common examples of hese effects: salt is used to melt ice on road Antifreeze is used to lower the freezing point and raise the boiling point of your engine coolant (waterand Freezing-point depression is also used by some organisms that live in extreme cold. Such creatures have evolved means through which they can produce high concentration of various compounds such as sorbitol and glycerol. This elevated concentration of solute decreases the freezing point of the water inside them, preventing the organism from freezing sold even as the water around them freezes, or the air around them is very cold Examples include some species of arctc- living fish, such as rainbow smelt, which can survive in freezing temperatures for long periods. In other animals, such as the spring peeper frog. the concentration of the solute is increased temporanily as a reaction to cold temperatures. In the case of the peeper frog, freezing temperatures trigger a large scale breakdown of glycogen in the frogs liver and subsequent release of massive amounts of glucose into the blood. The high concentration of glucose in blood causes a depression of the freezing point of the blood in peeper frog Substances are usually classified as ionic or covalent, or more precisely, electrolytes and non-electrolytes. Electrolytes dissolve in a solvent to give ions (charged particles) in solution while non-electrolytes dissolve to give molecules. A mole of non-electrolyte such as ethanol would dissolve to produce a mole of ethanol molecules. However, a mole of sodium l) would dissolve to form two moles of ions (Na and CI) Because colligative properties are related to the number of solute particles, we would expect a mole of NaCI to have twice the effect as a mole of ethanol. The number of particles that a given solute generates in solution is described by the i, the vant Hoff factor which is given by the following equation i-sum of moles of ell particles in solution moles of solute dissolved Thus, for ethanol and other non-electrolytes is1, while for NaCii 2. The vant Hoff factor is not necessary an integer. For substances that do not dissociate completely when dissolved the vant Hoff factor is not an integer. For example, the vant Hoff factor is not a whole number for the week acids and the weak bases that are dissolved in water. Also, for substances that form dimers the vant Hoff factor will be less than 1. For instance, dimers can be formed when the molecules of a solute make hydrogen bonds with each other in a non-polar solvent
oectrolyte solute is less than that of the pure solvent This effect is expresso states that the freezing point differs from that of the pure solvent by The quantatively bytheoi amounts that are e directly proportional to the molal concentration of the solute. In its general form this equation is written s the treezing point depression defined by Eq. 2 (see below), is the vant Hoff factor (see below), K, is the t depression constant that is specific for each solvent, and m is the molality of the solution and is expressed AT.K m (Eq. 1) In Eq 1, ΔΤ, freezing point freezing t moles of solute per kilogram of solvent (Eq 3). For water, K-1.86 Cimolal moles of As mentioned above: and T, is the freezing point of the pure solvent, also in °C. It is very Where, T, is the freezing point of the solution in C important to not confuse the actual freezing point with the freezing point depression! While molality is defined as 3) kg ef solvent Because moles of solute rass of so solete Eq. 4 equation 3 can be written as follows Eq. 5) Melar Mass ef solateKg ed solvent) By combining equations 1, 2 and 3 one can determine expenimentally the Molar Mass, MM (also known as molecular weight, MW) of an unknown solute of known mass in four steps: 1: the freezing points of the pure solvent and of the solution are measured 2n the AT is calculated from Eq 2 3d: the molality is calculated from Eq.1 4th: the Molar Mass of the solvent is calculated from Eq. 5 Also, by determining the freezing point depression for a solution, one can determine if the solute behaves as an electrolyte or a non-electrolyte in a particular solvent, ie the vant Hoff factor of the solute can be calculated using Equation 1. NOTES 1. Molality is defined as the #moles of solute kg of solvent) while molanty is defined as the (# oles of solute volume of solution). Eq. 1 uses molality for colligative properties because the colligative properties depend only on the number of particles in solution. The number of particles is measured in moles. Molality does not depend on the temperature as molarity does. If the temperature changes, then the volume changes slightly and the molarity can change. Also, the final volume of the solution will depend on characteristics of the solute as it goes into solution. The solute takes up some space and changes the volume, whereas if the mass of the solvent is used the molality will stay constant 2. Molecular weight or molar mass (MM) has units g/mol. MM is inversely proportional to molality and AT,. Molecular 3. AT, which is the change in the freezing point and it should not be confused with Tr which is the freezing point of the Mass should not be confused with mass (weight) which has units of grams (g) solution the type of the solute in a solution (electrolyte or non-electrolyte) b) the molecular In this experiment you will determine: a) weight solution of the unknown solutes tof an second unknown non-electrolite compound by measuring the freezing point depression of an aqueous GRAPHICAL M ETHOD USEDTODETERMİNETHEFREEZINGPONT
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Before You Come to Lab: .Print and Read the entire lab procedure sheet Safety in the Laboratory Safety glasses must be worn at all times while in the laboratory . Long pants and sleeves, closed toe shoes must be worn Glassware Look for glassware that is ask your instructor or TA for what you need needed in the drawers at your working areas. If you cannot find them there, then Ater completion of the lab, clean and return all glassware to their storage areas Waste Disposal and Cleanup All samples from the freezing point depression lab can be discarded in the sink Upon completing the lab, all glassware must be wa storage areas * . I shed with soap and water and let them dry at their *All stirning plates must be turned off, unplugged and returned to their storage area Return all stirring magnetic bars to their storage area Before You Leave the Lab . Wash your hands .Table 1 must be completed and signed by the instructor to confirm completion of the experiment Lab Reports Cover Page, Answers to Background/Conclusion/Critical Thinking Questions, Tables, Graphs, Calculations Materials: 2 of 1L Beaker or 600 mL Beakers 6 Large test tube 2x8 g Unknown non-electrolyte solute 2 Thermocouple 2 Magnetic Stirring bar 2 Magnetic Stirring plate . . .Ice Rock salt EXPERIMENTAL PROCEDURE In a nutshell Work in group of 6. Each student should make at least one trial. At the end of experiment, each member of the group should have 2 data sets of water solute A/solute B . Prepare for each trial an ice-salt bath with the temperature to range from-5℃ to-10°C . In a dry clean test tube add 20 ml DI water, a stirring bar and a thermocouple . Place the test tube in the ice-salt bath and measure temperature (°C) every 30 sec till 6 reading are equal to each other Repeat with a second sample of DI water In a dry clean and weigh test tube, add 20 ml DI water and weigh the tube with the added water Add 8 g of the unknown solute, a stirring bar and a thermocouple. Stir the solution til solute is completely dissolved Place the test tube with the solution in a new ice-salt bath. Record temperature every 20 sec until the solution solidifies . . . Repeat with an ice-salt bath and a fresh solution of the unknown solute
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